Lid of Boston Marathon pressure cooker bomb was found on sixth floor rooftop of hotel 35 yards away - and guests thought it was a hubcap

New crime scene photographs from the first blast confirms that a pressure cooker was used in the device

Lid of pressure cooker found on rooftop of building 35 yards away



Other photographs submitted to the FBI reveal the scene before and after the second bomb detonated



Devices were designed to act as 'Claymore' anti-personnel devices - which are meant to maim on the battlefield



An orange and grey bag can be seen on the opposite side of barriers to spectators before the second blast

The pressure-cooker bombs were packed with shards of metal, nails and ball bearings

Devices are frequently used in Afghanistan, India, Nepal and Pakistan, according to Homeland Security


The force of the first blast at the Boston marathon was so strong, the lid of the pressure cooker bomb was found on the sixth-floor roof of a hotel 35 yards away from the explosion site and is now a vital clue in the investigation.



A guest at the Charlesmark Hotel discovered the crucial piece of evidence just minutes after the blast. He picked up the twisted metal – believing it was a hubcap from a vehicle damaged in the bomb – and gave it to a policeman.



Twenty-four hours later he was quizzed by FBI agents, who revealed the mangled metal was one of biggest clues so far in the search for the terrorists who killed three and injured 183 others.

WARNING: GRAPHIC CONTENT AND VIDEO BELOW

The pressure cooker lid was found on top of the Charlesmark Hotel which is 35 yards away from the explosion site - such was the force of the blast

Map showing the Boston crime scene perimeter where experts are trying to piece together the clues left behind the deadly marathon explosion Forensic investigators look through the top of a building on Boylston Street for clues, two days after the bombs exploded just before the Boston Marathon finish line Investigators are still combing through the area for more vital clues to try and find the person or persons responsible for Monday's bomb

Hotel owner Mark Hagopian said: 'One of the guests had been up on the roof earlier in the day. Immediately after the blast he went back up there and spotted what he thought was a hub cap.



'As it hadn’t been there earlier he thought it could have come from a damaged car, so he picked it up and took it downstairs.



'He handed it to a policeman and thought nothing more of it until the FBI contacted him and hotel manager Curt Butcher on Tuesday evening.



'They met for 35 minutes and the FBI confirmed that it was part of the pressure cooker bomb.'



Hogopian, 50, was hosting a marathon party for 100 people when the first bomb exploded on Monday afternoon.



As guests rushed outside the see what was happening, the second bomb went off just yards from the hotel’s outdoor patio.



'We were knocked off our feet by the blast and all around us there were bodies – seven or eight people missing limbs’ he said.



'There was blood splayed everywhere. It was utter chaos.



'One of the fourth-floor guests went up to the roof to see if he could see what was happening. That’s when he found what he thought was the hubcap.



'He handed it to the cop as everyone was being evacuated – at the time it was feared there were more bombs set to go off.

'Now it turns out that piece of metal is a big piece of the evidence. Apparently, forensics should be able to get many more clues from that.



'The FBI also took away video and photos the guest had taken. They are scouring those for further evidence.'



Bomb: The photos were produced by the Joint Terrorism Task Force of Boston and provided to Reuters by a U.S. government official who declined to be identified and show pieces of a stainless steel pressure cooker with an Underwriters Laboratory number. One picture shows the imprint: Gas and Electric

The devices are believed to be pressure cooker bombs — a commonplace cooking utensil in many countries — a piece of which is shown on the left along with remnants of the black nylon bag and on the right, pieces of the sophisticated detonator



Initial examination of the bombs revealed they appeared to utilize battery packs and circuit boards, which indicates a sophisticated triggering mechanism with an 'egg-like' timer.

'It appeared to be built from scratch but with a sophisticated triggering mechanism. And frankly, at the end of the day, all bombs are crude devices, and it is the way they are triggered that can be sophisticated,' said one official with strong knowledge of explosives. 'They functioned as designed.'

Low quality explosive ingredients may have been the bombs’ key components, according to an unnamed expert quoted by CNN. That would explain the yellowness of the flame, as shown in video and photos of the event.

Higher-quality military explosive is usually gray or black, said the expert. Photographs taken by a member of the public of the second bomb site before and after detonation show an orange and grey bag next to the barrier - right where the bomb appears to have gone off. Detectives are now investigating the possibility that this bag contained the device that exploded with such devastating effect.

However images and fabrics from the remains of the bomb shows they were kept in black nylon duffel bags so it is as yet unclear if the bomb was in he gray and orange bag.

Investigation: Officials survey the site of a bomb blast on Boylston Street in Boston searching for evidence that might help them find a suspect or suspects Second Bomb: Photos show a bag next to a mailbox along the marathon route and may have been the footage used by the FBI to positively ID a suspect Shocking: Seconds after the bombs went off on Boylston Street there is no sign of the bag, the picture is blurred because of the graphic nature of the content Vigils were held overnight as hundreds of people gathered to remember the victims, the third of whom was named yesterday as Chinese Boston University student Lü Lingzi. Lingzi was attending the Boston marathon with her friend Zhou Danling, a student of actuarial science at BU, who was originally said to be in a coma at Boston Medical Center but showing signs of improvement after suffering serious injuries in the blast . The other two fatalities in the bombing have been identified as eight-year-old Martin Richard, the son of a Dorchester community activist, and 29-year-old restaurant manager Krystle Campbell.

A five-year-old boy is still critically injured at Boston medical center.

A law enforcement official told CBS News that the two bombs that exploded were made to look like discarded property.

Earlier in the day, lead FBI agent Richard DesLauriers confirmed that items from the first blast have been recovered and are being sent to a special facility at FBI headquarters in Quantico for study - in the hope that they will lead them to the killer or killers. He also admitted the investigation into those responsible was in its 'infancy' and that the range of suspects remained 'wide open'. More than 2,000 tips from the public were reviewed and analyzed in the first 24 hours but no individual or group has yet claimed responsibility for the attack. The FBI has issued a plea to members of the public for help in the hunt for clues saying: 'Someone knows who did this'.

He said among those items were 'pieces of black nylon which could be from a backpack and fragments of BBs (ball bearings) and nails possibly contained in a pressure cooker device. RELATED ARTICLES Previous

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Obama insists federal government 'will get to the bottom of'... Share this article Share 'The bag would have been heavy because of the components believed to be in it. We won't know with certainty until the laboratory completes its final review.' The second device was also housed in a metal container says the document, but so far there is not enough evidence to confirm for certain if a pressure cooker was also used. 'Someone knows who did this,' added Richard DesLauriers, the special agent in charge of the FBI’s Boston office.

'Importantly, the person who did this is someone’s friend, neighbor, coworker or relative. We are asking anyone who may have heard someone speak about the marathon, or the date of April 15, in any way that indicated that he or she may have targeted this event to call us.' DesLauriers added: ' At this time, there have been no claims of responsibility.'

Saying that the bomber or bombers most likely dropped the bags easily amongst the commotion during the race, Rossini said that the FBI will be looking to the remnants of the bags to lead them to the killers.



Rossini, however, cautioned against jumping to any conclusions that the bombing was the result of Islamic-inspired terrorism. 'It could be a white supremacist group. We just don’t know.'

The Shenyang Evening News reported Wednesday on its official Twitter-like microblog account that the victim is named Lü Lingzi. An editor at the newspaper says that Lü's father confirmed his daughter's death

People gather for a vigil for the victims on the Boston Common as an investigation continues into dual bombings at the Boston Marathon finish line in Boston, Massachusetts, on Tuesday

A member of the National Guard and a Boston policeman direct a man away from a barricade near the finish line of the Boston Marathon in Boston on Tuesday

People stand during an interfaith prayer service remembering the victims of Boston Marathon bombings at the Paulist Center on Tuesday evening in Boston, Massachusetts



Disaster: Mourners attend candlelight vigil for Martin Richard at Garvey Park, near Richard's home in the Dorchester section of Boston, on Tuesday, April 16

Vigils were held overnight as hundreds of people gathered to remember the victims, the third of whom was named yesterday as Chinese Boston University student Lü Lingzi

The bombs used to kill and maim are believed to have contained black powder or gunpowder as the explosive, and information on how to make such a bomb is available on the internet, experts said. The devices were then left at the scene to look like discarded property, CBS News reported.



Investigators have also found pieces of an electronic circuit board which could indicate a timer was used in the detonation.

Although no group has yet claimed responsibility for the attacks, similar devices were used in the failed 2010 attempt to bomb Times Square by Faisal Shahzad, who admitted he had undergone bomb-making training at a militant Islamist faction camp in Pakistan.

A pressure-cooker bomb is also a preferred weapon of al-Qaeda and listed as the 'most effective' weapon of jihad, according to an English-language terror magazine called Inspire, in an article entitled 'How to Build a Bomb in the Kitchen of Your Mom'.

Another article in Inspire last year listed 'the most important enemy targets' for jihadists in America - and included sporting events, CNSNews noted.

The aim should be to target 'human crowds in order to inflict maximum human losses,' a terrorist known as Abu Musab al-Suri wrote. 'This is very easy since there are numerous such targets such as crowded sports arenas, annual social events, large international exhibitions… etc.'

Bomb: Images from a Homeland Security Department pamphlet shows a diagram for rudimentary improvised explosive devices using pressure cookers. Police sources have revealed that the deviced used in the Boston Marathon bombings on Monday used pressure cookers filled with shrapnel and ball bearings



Killed: Eight-year-old Martin Richard from Dorchester, Massachusetts was among the three people killed when two bombs detonated at the Boston Marathon on Monday Loss: Krystle Campbell, pictured, also lost her life in the terrorist attack. Doctors originally confused her identity with a friend, so her parents believed she was alive



Martin Richard, 8, who was waiting at the finish line with his father, mother and siblings, was among those killed when the two bombs detonated at the crowded sports event. His mother has undergone brain surgery and his six-year-old sister lost a leg. His 12-year-old brother escaped injury.

Neighbors told MailOnline about the moment Martin Richard's father, Bill, returned home still wearing hospital scrubs on Monday night and looking like the 'walking dead' as he struggled to come to terms with his son's death and injuries suffered by his wife, Denise, and daughter, Jane.

In a statement released on Tuesday, he said: 'My dear son Martin has died from injuries sustained in the attack on Boston. My wife and daughter are both recovering from serious injuries.

Blast: Runners continue to run towards the finish line of the Boston Marathon as the first of two explosions erupts near the finish line of the race

Exact Moment: People react as the second explosion goes off near the finish at the Boston Marathon finish line on Monday, sending authorities out on the course

'We thank our family and friends, those we know and those we have never met, for their thoughts and prayers. I ask that you continue to pray for my family as we remember Martin. We also ask for your patience and for privacy as we work to simultaneously grieve and recover. Thank you.'



Doctors confused another victim, Krystle Campbell, 29, with her friend, so for hours her parents believed she was alive and undergoing surgery. Only when they went to visit her in hospital, did they realize the patient was not their daughter .

Loved: Peace is written on the sidewalk in front of the Richard house in the Dorchester neighborhood of Boston, left, while neighbors embrace in the street

Sympathy: Flowers and gifts are left by loved ones outside of the Richard family home in Dorchester, Massachusetts on Tuesday morning First pictures: Martin was killed in the first explosion as he waited to give his father a hug at the finishing line. His sister and mother were also injured Tragic: Martin Richard, right, is pictured with his family. His mother, Denise, has undergone brain surgery and his six-year-old sister Jane lost a leg in the blast, while his older brother, Henry, 12, escaped injury. They are also pictured with his father, Bill