Video and pictures show a dusty basement in Sheikh Najjar is strewn with blankets, tattered mattresses, cardboard, plastic bottles and other

This is the first glimpse inside the secret underground prison where ISIS caged Western hostages - including James Foley, Steven Sotloff and David Haines - former fellow prisoners have claimed.

Freed captives told MailOnline they lived in wretched conditions alongside them, half-starved on hard concrete floors in almost permanent darkness in the basement room of the abandoned factory in the Sheikh Najjar Industrial City, in the suburbs of Aleppo, during the last four months of 2013.

They were then moved to Raqqa, Syria, where they were handed over to their executioner, the infamous 'Jihadi John' and his death squad.

The former prisoners gave a chilling insight into the ordeal that the men - and allegedly one woman - endured in the bleak darkness.

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Hellish: A Syria TV reporter took this image in an abandoned factory turned ISIS prison in Sheikh Najjar, Syria - unaware that later it would be claimed that it was where Western hostages were kept for months

Separated: One hostage claimed that the basement was divided into two different sections; the first was converted into about 14 dingy single cells and the second into 12 single cells and three big rooms

Together in the dark: It is claimed that the Western hostage men were kept together in one of the larger rooms

One of the former hostages who talked to MailOnline identified the dungeon - either a disused wood or furniture factory - from footage broadcast by a pro-Syrian TV Channel earlier this year, after President Bashar Al-Assad's forces pushed out Islamist rebel groups from the heavily contested area.

But the Syrian reporter walking through the ISIS prison - before the world was revulsed by the video of Jim Foley's execution in August - had no idea that it had housed nearly 20 Western journalists and aid workers.

As he walks through, he points the cameraman to discarded blankets, tattered mattresses and plastic water bottles that are strewn around the dusty floor in the footage - haunting evidence of the miserable existence of the prisoners who had been caged there.

The reporter also posted images of his visit to the Sheikh Najjar prison to his Facebook page, showing the cubicles in which some of the prisoners were believed to have been kept.

A shocking separate image he uploaded on the same day shows a chair apparently used to restrain prisoners with belts, but it's not clear whether this picture was taken in the factory.

The movements and ordeal of ISIS' valuable foreign hostages - used either for ransom or propaganda - have been shrouded in mystery and speculation for more than a year.

The apparent location of where many of the Western prisoners spent long periods of their captivity came from interviews with two European hostages, freed earlier this year after ransoms were reportedly paid.

And a Syrian prisoner who spent two months in Sheikh Najjar identified the location from the TV report. He said he regularly heard the American and European prisoners, including Jim Foley, from his nearby cell.

ISIS, according to the Syrian, had divided the basement into two different sections; the first was converted into around 14 dingy single cells and the second into 12 single cells and three big rooms.

The foreign aid workers and journalists spent most of their time together in one of the big rooms, he said, while most of the Syrians were housed in the individual cubicles. An American woman was held in a separate cell in the same location, it is claimed.

Courage: The Syrian remembers Jim Foley as a cheerful and funny interlocutor, frequently bantering with the guards and cajoling them into better treatment. This was before he was handed over to Jihadi John

Cameraderie: David Haines, left, was part of the congregation of western hostages at Sheikh Najjar. As was American-Israeli journalist Steven Sotloff, right. One hostage said that as Sotloff secretly observed the Yom Kippur fast by pretending to have an upset stomach, he kept his eggs for him that had been served that day

Desperate: British photojournalist John Cantlie, who is apparently still alive and has appeared in numerous ISIS propaganda videos, was believed to be in the Sheikh Najjar prison in October 2013

A freed European hostage claimed: 'They built the prison around us. When we came in, there was nothing there. It was just a normal factory.'

The room where the male hostages spent their time was 'about five metres by five metres, with a toilet, but not really square', he said.

Conditions were grim. Many of the prisoners were in a state of constant hunger and the basement was freezing cold.

'Only in Raqqa did they decide to feed us', one of the European hostages told MailOnline - referring to the Syrian city that is the headquarters of ISIS - where the prisoners were moved to later.

We had eggs that day, and eggs were very important food to keep. He didn't say he was doing Yom Kippur to the other ones, only to two people. Because I saw him doing it, I said "are you doing Kippur?". He said 'how do you know? Prisoner on American-Israeli Steven Sotloff's secret fast

Candles were only brought when it was time to eat, according to the Syrian prisoner, which wasn't very often.

The European arrived in the Sheikh Najjar prison on August 29.

It was in Sheikh Najjar that Steven Sotloff quietly observed the Yom Kippur fast weeks later by feigning an upset stomach, said the European.

Sotloff, an American-Israeli who hailed from Florida, had been kidnapped in Aleppo province in August. A video of his beheading was released by ISIS on September 2 this year.

The European hostage told MailOnline that he kept Sotloff's eggs for him that had been served up by their captors that day.

'We had eggs that day, and eggs were very important food to keep. He didn't say he was doing Yom Kippur to the other ones, only to two people. Because I saw him doing it, I said "are you doing Kippur?". He said 'how do you know?'.

The hostage remembers being put in a room on October 5 with Jim Foley and British photojournalist John Cantlie. Also there around that time was British aid worker and father-of-two David Haines, who was kidnapped in early 2013 and executed by Jihadi John this September.

Both Haines and Cantlie, who is apparently still alive and has appeared in numerous ISIS propaganda videos, had spent the early period of their captivity with the British jihadis before being transferred to the eye hospital in Aleppo city. All would end up in Shekih Najjar.

Hostages were collected from different parts of Northern Syria and added to the group; by the time they left Sheikh Najjar, they numbered 19, it is claimed.

Restraint: The reporter also uploaded this picture on the same day as the factory visit of what looks like a chair used to restrain prisoners. But it has not been confirmed that it was at the alleged prison site

Grim: The conditions were extremely basic. There was hardly any light and it was extremely cold at night

Starving: Food was rarely served, said one Syrian prisoner. When it was served it was by candlelight - a rare moment of light in the gloom

Beatings: A former prisoner claims that the Western prisoners were treated relatively well, given their situation. But Syrian prisoners held with them were beaten and one Russian was treated especially harshly

Treatment: Some guards gave the Western hostages extra bread, jam and sweets, said a Syrian prisoner

Tortured and shot: Russian prisoner Sergey Gorbunov was marked out for particularly harsh beatings by a Chechen guard. He was eventually shot dead and pictures of his body was shown to prisoners and their families to intimidate them

Almost everything was audible in the darkness. Peering through the darkness from a hole in his cell, the Syrian said that he'd heard American and European voices, including that of Jim Foley, 40.

'Maybe he was the oldest there', said the Syrian, who said that Foley had become one of the leaders of the hostages who conversed with the guards on their behalf. 'He was always talking in the name of the group, so I heard him more than anyone else.'

The Syrian remembers Jim Foley as a cheerful and funny interlocutor, frequently bantering with the guards and cajoling them into better treatment.

'Once they brought them clothes and T-shirts and stuff, and gave it to them. And he said "Oh thank God, these are the first new clothes for two years."'

Like many of the other Syrians there, the prisoner MailOnline spoke to was tortured in the first weeks of his captivity.

Many of the guards were mostly either French or French-speaking, or Belgian; the same sub-group of ISIS militants who'd held them for several months in Aleppo city.

Whereas their prison chief in Aleppo city had been a lanky Dutch Moroccan engineer called Abu Ubaida al-Magribi, the head of the prison in Sheikh Najjar was a French Tunisian who went under the name Abu Mohammed al-Franci. He was more French than Tunisian; he didn't seem to know any Arabic.

'He was nice to some and tough with others', recalls the Syrian prisoner. 'He tortured some people himself.'

None of the Western prisoners were tortured while in Sheikh Najjar, though many of them had been before they arrived.

He was always talking in the name of the group, so I heard him more than anyone else - Syrian prisoner on Jim Foley

It has been reported that Jim Foley and John Cantlie had already been beaten, waterboarded and brutalized in their first encounters with the British kidnappers known as 'The Beatles', including Jihadi John, in the first six months after their kidnapping.

But the time they spent with European and Syrian guards in Sheikh Najjar and in Aleppo city must have been one of relative relief.

Many of the guards were friendly, says the Syrian prisoner, especially with the foreigners.

'Some of the Syrian guards were nice with the foreigners – they used to bring them sweets, jam, and extra bread.'

One exception however was a Russian called Sergey Gorbunov, who arrived separately in Sheikh Najjar, having been kidnapped by one of several volatile sub-groups which went on go on to create the nucleus of ISIS.

Timeline of captivity: It is thought that most of the Western hostages were imprisoned from July to August 2013 at an Eye hosptial in Aleppo, then were moved to the wood or furniture factory in Sheikh Najjar from late August/beginning of September to December 2013. Then they were moved to at least three different prisons in the ISIS de facto capital of Raqqa for most of 2014

Devastation: Sheikh Najjar (above in March) has been the scene of intense fighting between rebels, ISIS and forces loyal to Syrian president Bashar al-Assad

Hope: A former hostage told MailOnline that they heard almost constant gun battles overhead and not far away as they were caged underground

Even before he arrived at the prison, according to one of the European hostages, it was clear that he'd been badly tortured.

On two or three occasions while there, says the Syrian, a Chechen guard took him outside the communal cell into the corridor, where he could hear him being beaten.

'They took him from inside the cell, out into the corridor. He was beating him with his fists', said the Syrian.

In the end, Mr Gorbunov was shot dead in the first week of March 2014 in Raqqa, simply because he had no value to his captors.

We need to make sure you will be in a secure situation, to make sure any other groups don't take you again. This trip will take two or three hours, so please be patient. You will be with your families by tonight Cruel lie told by ISIS prison supervisor

The picture of his bullet-riddled body was sent to the families of some European hostages to add impetus to their demands for millions of euros in ransom money - and shown to the remaining hostages to terrify them into submission.

The hostages were ushered out of their basement on December 23 and Christmas Eve; their captors were now in a hurry.

The Sheikh Najjar Industrial City was the scene of heavy fighting between the Syrian regime and various Islamist groups.

The frontline was constantly changing and the prisoners remember hearing the fighting going on not far away above ground.

The day that the Western hostages were herded off, the Syrian prisoner remembers hearing lots of activity after morning prayers. The foreigners were given new clothes.

Abu Maryam, a Syrian from the Iraqi border area who was in charge of supervising ISIS's prison network and a close associate of Al-Magribi, arrived to make an announcement.

'We are sorry', he told the assembled hostages, via a translator. 'It is wartime; we don't know our friend and we don't know our enemy, but we are going to release you soon. Please be patient. We will take you to the Turkish border.

'We need to make sure you will be in a secure situation, to make sure any other groups don't take you again. This trip will take two or three hours, so please be patient. You will be with your families by tonight.'

It was another cruel trick. After two short pit stops, they'd be taken to ISIS's stronghold in Raqqa. Their numbers would soon swell with half a dozen fresh hostages, including executed aid worker Alan Henning – and where Jim Foley, John Cantlie and David Haines would be reunited with their most cruel tormentors in the form of British guards and Jihadi John.

Alone: A female U.S. hostage was held in one of the many separate cubicles in the basement, it is claimed

Propaganda: The TV report showed ISIS pamphlets found in the alleged prison after Assad's forces pushed the Islamic militants out of Sheikh Najjar Industrial City

Cat and mouse: Those searching for the hostages had allegedly been aware of a 'wood factory' in Sheikh Najjar being where they had been moved to. But by that time the prisoners had been moved on

As the prisoners kept their hopes up as best they could during their captivity, those desperately searching for them were playing a game of cat and mouse that they were eventually to lose.

According to the testimony of freed European hostages, the ISIS prisoners began to arrive in the summer of 2013 in an Eye Hospital in Aleppo, Syria.

In the same large compound two American prisoners Matthew Schrier and Theo Padnos, had been hostage for some months in a Children's Hospital by the Al-Qaeda affiliate Jabhat al-Nusra. They were later freed.

Jim Foley and John Cantlie were first sighted in the Eye Hospital in July 2013 by another European hostage.

It has been reported that special forces mounted a raid to rescue the prisoners from the compound. But by the time that information was passed to investigators in November, the prisoners were long gone.

Beginning in late August through the first week of October, they had quietly moved out of Aleppo city to the new location in Sheikh Najjar Industrial City.

To investigators, the suspicion that they had been moved to Sheikh Najjar facility had been clear for some time.

Yosef AboBaker, the rebel activist who accompanied Steven Sotloff into North Syria and who was kidnapped for 15 days before being released, began making his own enquiries about the location of his friend soon afterwards.

In an interview in Antakya, Turkey, in March 2014 he said that 'the interesting information is coming from Sheikh Najjar', where the hostages had been seen by another released Syrian prisoner in a 'wood factory'.

Once again, however, the information came too late – the hostages had already been moved.