
Olissa won't let her daughter in the back yard on her own. Not since a gang of drug traffickers tried to hide from US border patrol agents next to her home.

‘It was terrifying’, she said. ‘They were trying to get into the back door to hide.'

Olissa, of McAllen, Texas, lives two blocks from the border, and her home is less than a mile from the most dangerous Mexican border city, which has a higher murder rate than many war zones.

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Slaughter: Reynosa has been caught in the bloody vortex of a cartel war since 2010, which has cost the lives of more than 15,000 people

Death: Bodies are left strewn in the street in Reynosa as a warning to locals living in the city which has a murder rate as high as warzones

Fears: McAllen resident Olissa is scared for her daughter's safety after narcos hid from border patrol agents in her back yard

The city in the state of Tamaulipas has been caught in the bloody vortex of a cartel war since 2010, that has cost the lives of more than 15,000 people, many of whom are innocent civilians cut down in the crossfire.

The local police force was disbanded in 2013 because half of the police officers were killed in the tit-for-tat slaughter. Federal Police and the Mexican military now patrol the city with assault vehicles in armoured trucks.

The grip of gang violence is so bad on Reynosa, which has a population 600,000, that 950 murders were committed in 2013 - a rate of 150 killings per 100,000. In comparison, across Iraq in 2012, the homicide rate was eight per 100,000.

Less than a 10 minute drive away, there were only two murders in McAllen, Hidalgo County, in 2013. But frequently, the Texan residents can hear gunshots at all hours of the day and even spot heavily-armed drug smugglers in their streets after dark.

And ruthless cartels target anyone standing in the way of their miserable business.

Less than a 10 minute drive from Reynosa in Mexico is McAllen in Texas, US, and residents can hear gunshots at all hours of the day

Damage: Buildings are riddled with bullet holes and covered by cartel graffiti, and nearly half the city’s storefronts have been abandoned

‘The cartels pay a bounty of $20,000 for a US border agent, dead or alive’, a reporter in Tamaulipas, who wished to remain anonymous because of fears of retribution, told MailOnline. ‘As the business of trafficking drugs gets harder, the cartels are willing to take more and more extreme steps to move their product into the United States’.

‘I would never cross the border into Mexico, it’s unbelievably dangerous over there’, Olissa said.

Despite the police arriving within minutes to stop the traffickers in her garden, she says the experience left her traumatised and terrified for her family’s safety.

‘Those criminals make a lot of money from human trafficking,' she told MailOnline. 'I’m terrified for my baby living so close to the border.'

Reynosa visually bears the scars of its violent history. Public buildings are riddled with bullet holes and covered by cartel graffiti, and nearly half the city’s storefronts have been abandoned because business owners have fled from cartel extortion.

After dark the streets are empty, except for pistol-toting cartel lookouts whispering into their radios.

Desperate: Homeless people in Reynosa are paid by the cartels to act as lookouts and they often cover their faces to avoid identification

Gravedigger: The town's gravediggers says the cemetery is running out of space, and that he digs on average 20 graves a week

Solace: Sister Nidelvia Avila runs the migrant shelter in the crime-torn Aquiles district of the city, just a stone’s throw from the border fence

‘I regularly hear gunshots being fired from my bedroom’,' said Hidalgo County resident Suehay, who has lived on the US-Mexico border all her life. They can go off at any time, but it’s far more common to hear them on weekends and public holidays.'

Suehay has family in Reynosa and used to visit regularly. However, since her uncle was murdered by cartel killers three years ago after speaking out against the violence, she says she has been too terrified to go back.

‘You gamble with your life every time you cross the border’, she told MailOnline. ‘I worry so much about my family but there’s nothing I can do’.

Despite the threats, Hidalgo County Sheriff Eddie Guerra and his team say they’re on top of the situation.

‘We’ve got a good relationship with our local community, who have recently been instrumental in tipping us off when it comes to events at the border,' said Deputy Sheriff J.P. Rodriguez.

A 2014 study by research company Gallup named McAllen as the city with the highest rates of fear for safety after dark in the whole of the United States.

Reynosa: The streets of the city are covered in cartel graffiti and many of the public buildings are full of bullet holes following gun fights

McAllen: A 10-minute drive from Reynosa, Texan residents can hear gunshots all hours of the day and spot drug smugglers in their streets

It found less than half of residents were comfortable outside their homes after dark , despite the fact it had a lower violent crime rate than the US overall in 2012. More than 30 per cent of residents lived below the poverty line that year.

The US State Department warns against all-but essential travel to the Mexican state of Tamaulipas.

It says: 'Throughout the state violent crime, including homicide, armed robbery, carjacking, kidnapping, extortion and sexual assault pose significant safety risks.

'Law Enforcement is non-existent in many parts of Tamaulipas and violent conflicts can occur in all parts of the region and at all times of day’.

‘The cartel armies number in their thousands’, said the Tamaulipas reporter, ‘and they’re fighting a war with anyone who gets in their way.'

More than 600,000 federal crimes were reported in Tamaulipas state last year. There is a daily average of 6.8 homicides, 40% of which are concentrated in Reynosa. Some 2,500 people are murdered in the state annually.

On the day MailOnline visited Reynosa, four murders were committed. Two victims were 18-year-old girls who had been kidnapped, raped and then forced to consume rat poison.

Drugs: More than a tonne and a half of marijuana seized from a safe house in Reynosa - which has been caught in a cartel war since 2010

Gulf cartel members arrested in possession of narcotics and firearms (left) and a police vehicle involved in a shootout last year (right)

The narco blockades were set up across the city of Reynosa earlier this year following the capture of Gulf Cartel deputy El Comanche

Targets: A school bus is set alight by cartel members hoping to kill the children of their rivals in the conflict-torn Mexican city

The Reynosa administration, led by Mayor Jose Elias Leal, refused to comment on the town’s situation despite MailOnline’s repeated requests for comment.

The violence in Tamaulipas exploded in 2010 when the Zetas, the armed wing of the Gulf Cartel, broke away from the criminal organisation following a dispute.

The newly formed cartel, which became legendary for its brutal decapitations, began to fight the Gulf cartel for dominance throughout eastern Mexico.

Tamaulipas state’s three largest US-border towns, Nuevo Laredo to the west, Matamoros to the east and Reynosa in the centre, became important strategic territories for the business of drug smuggling.

While Nuevo Laredo became Zeta territory and Matamoros the base for the Gulf Cartel, Reynosa’s location between the two warring cartels turned it into a battleground, and the city’s streets quickly ran red with the bloodshed.

Narco blockades were set up across the city earlier this year following the capture of Gulf Cartel deputy El Comanche. Today it is believed the cartel, led by Juan ‘The Bull’ Loiza, controls Reynosa.

Yet since the Mexican military’s heightened campaign in Tamaulipas from 2013, the business of drug trafficking has become more difficult and the narcos have turned to the local population to make up their losses.

Grief: Rosa Perez still mourns the loss of her son after he was killed last year - he was robbed at gunpoint while leaving the cinema

Gone too soon: The municipal graveyard in Reynosa is filled with the graves of those who died young during the city's cartel conflict

Scared: Suehay regularly hears gunshots coming from south of the border, just 200 yards from her home in Hidalgo county. She used to visit family there regularly until her uncle was gunned down by the cartels three years ago

‘Since the government sent the military in, federal crimes such as drug trafficking have decreased,' said the crime reporter. 'But without a local police force, we’ve seen street-level crime double.'

More than 16,000 carjackings and 33,000 cases of extortion were reported in Tamaulipas during the final three months of 2014.

Many residents use social media to warn friends and relatives about violent confrontations on their city’s streets, using the hashtag #ReynosaFollow.

However, this trend has been curbed following violent retributions against a number of Twitter users who denounced the violence online.

‘We’re living in the middle of a war,' said Sister Nidelvia Avila, who runs the migrant shelter in the crime-torn Aquiles district of the city, just a stone’s throw from the border fence.

Sister Avila sees more than 1,500 people, both migrants and deportees, pass through the doors of her refuge every month.

Tamaulipas, the most north-easterly state in Mexico, is a major passage for both Central American migrants to and deportees from the United States.

It’s estimated that while over 1,500 deportees arrive in Reynosa every month, a further 3,000 arrive from Guatemala, el Salvador and Honduras seeking to cross the border illegally.

Many of these people end up stuck in Reynosa, and with nowhere else to go and no chance at finding legal employment, end up falling in with the cartels who recruit them with false promises of money and power.

'They end up as slaves', says Sister Avila, who has seen the vicious circle of crime affect many of the people who sought shelter at her migrant centre.

‘We get a lot of the low-level cartel here for our charity breakfasts and they are miserable’, she says, 'many are turned into slaves by being forced into drug addiction, and all are terrified of the cartel leaders’.

‘There’s not much I can do to help them. I can't offer them shelter again where they’ll mix with the other guests because the cartel will infiltrate here before you know it’.

She adds: ‘We don’t advise them to step even a foot outside of our compound,' she told MailOnline. 'The cartels get hold of them with promises of money, but they end up enslaved.

'The rare ones who escape tell stories of being blindfolded, drugged, tied up and being used either as mules to carry narcotics over the border or as cannon fodder in their war.'

Hidalgo County Sheriff Eddie Guerra (right) and his team, including deputy J.P. Rodriguez (left) say they’re on top of the situation

Eduardo (left), a deportee from Florida, had not stepped outside the migrant shelter run by Sister Nidelvia Avila since his arrival

Eduardo, a recent deportee from Florida, had not stepped outside the migrant shelter since his arrival. He says he plans to return to his home state of Queretaro without delay.

‘I’m terrified of Reynosa,' he said. 'At night I lie in bed and hear gunshots and screams from the street outside.'

One tortilla salesman in the dangerous district of Aquiles told of his struggles to keep the business afloat while dealing with extreme extortion at the hands of the cartel.

‘I have to pay 40% of all my earnings to them,' he told MailOnline. ‘Selling tortillas isn’t very profitable and there have been times that I’ve had to sell all the food rather than feed my family just to avoid trouble. It’s death if I don’t pay.'

Beside his tortilla shop, the cartel lookouts kept a close eye on the customers moving in and out, as well as the length of the street they guard for their cartel paymasters.

‘We stay in this spot all day and night,' one of them told MailOnline, his face covered by a surgical mask to hide his identity. ‘If we see any cars or people we don’t recognise then we make a phone call.'

’The police haven’t been around this part of the city in years,' he said, laughing.

Murder: The bodies of soldiers lie in the streets of Reynosa, Mexico, after they were killed during a shootout with cartel members

The police force disbanded because half the officers were killed in the conflict - the army and Federal Police now patrol's the city's streets

Cartel members display their wealth with photos such as this. Big cats, fast cars and wads of cash are usually shown off on social media

The violence in Tamaulipas exploded in 2010 when the Zetas (graffiti pictured), the armed wing of the Gulf Cartel, broke away from the criminal organisation following a dispute

The gravedigger at Reynosa’s municipal cemetery, Horacio Fuentes, said he can barely deal with the constant influx of bodies.

‘I bury around twenty people a week, and most of them are far too young,' he told MailOnline. ‘The ones we can’t identify go into the common graves but soon we’re going to have to start cremating them; we simply haven’t got the space.'

Rosa Perez lost her 21 year-old son to the ‘unending violence’ last year.

Luis Alfredo Rodriguez was robbed at gunpoint while leaving the cinema with his girlfriend. When their assailant attempted to kidnap his partner, Luis fought back and was shot six times in the chest and abdomen.

His girlfriend was discovered dead three days later, her mutilated body dropped from a moving vehicle outside the cinema where Luis had been killed.

Sitting by his grave in the town cemetery, Rosa says she sees no end to the violence.