reported one inmate as saying: "Prisoners are walking around with knives and coshes. They've nicked mobile phones out of the office, everything's been smashed.
"We've got control of the prison. It started off as a little joke about. But now every wing is open."
Reports suggest inmates have destroyed prison guards' offices, stolen supplies from the prison medical unit and lit fires in the jail.
Former inmate Tyler Johnston, 21, said prisoners took batons, raided safes containing phones and drugs, and locked other prisoners inside cells during the riot.
Speaking outside the jail, the convicted drug dealer said: "The prisoners were running it last night, not the screws. When I was inside I had to break up fights 'cause there wasn't enough staff.
"Bedford Prison is falling apart. There's cockroaches everywhere, the floors peeling off - it's an absolute state. When you put people under that much strain they're going to bite.
"They took batons, raided safes with all the drugs and phones, and merged A and B wings. Boys were getting locked in their own cells."
Another man said his relative called him from inside using a contraband phone.
He said: "He told me it all started in C wing when staff got into a dispute with a young inmate.
"It seems like he was roughed up a bit and then his mates got involved and it all kicked off.
"They got the keys off a prison officer and that's how it started."
A prison riot involving up to 300 inmates has broken out at HMP Bedford Credit: GEOFF ROBINSON PHOTOGRAPHY Security services could be seen operating a crane over the prison walls on Sunday night Credit: GEOFF ROBINSON PHOTOGRAPHY The relative went on: "This riot isn't about problems between inmates. What's happening is aimed at the staff because the inmates are fed up with the conditions in the prison.
"Prisoners are locked up for 23 hours a day and just get half an hour to walk around a synthetic football pitch and then it's back to the cells.
"Conditions in that jail are terrible. There is no space and not enough staff.
"It was only a matter of time before this happened. Everyone know something like this was going to take place.
"Weekends are especially bad in the prison because there isn't the staff on duty. There is no proper food available and you end up with a filled roll and a packet of crisps if you are lucky."
There were no injuries to prison staff but two inmates were treated for injuries - one with a suspected broken jaw and the other for chest pains.
Today dozens of prison vans were transferring lags to other jails around the country.
The prison service confirmed the incident had been resolved late on Sunday night.
A spokesman said: "Specially trained prison officers and staff from the emergency services have successfully resolved an incident involving a number of prisoners at HMP Bedford.
"An investigation into this incident will take place.
"We are absolutely clear that prisoners who behave in this way will be punished and could spend significantly longer behind bars."
Richard Fuller, MP for Bedford and Kempston, will put an "urgent question" to Justice Secretary Liz Truss in Parliament today.
Shadow Justice Secretary Richard Burgon tweeted: "More troubling news concerning our prisons.
"The Justice Secretary needs to do more urgently to tackle crisis."
Ambulances and police were at the scene tonight as scores of prisoners rioted at the Category B unit Credit: GEOFF ROBINSON PHOTOGRAPHY HMP Bedford was opened on its present site in 1801 and currently houses around 500 inmates.
The jail was described as an “abject failure” by the chief inspector of prisons Peter Clarke in September.
A report revealed it was easier for inmates to get drugs than clean sheets or clothes , and standards had fallen to "unacceptable levels".
An inspection in May also found that the physical condition of the prison was poor, with many inmates living in cramped conditions. The report detailed damaged furniture, graffiti, shortages of clothing and dirty, unscreened showers.
The report also said: "Arrangements for managing violent and bullying behaviour and supporting victims were weak."
In July we revealed convicted robber Craig Lynch boasted of his cushy life inside HMP Bedford as he set up a Facebook group for lags to swap tips on smuggling phones and drugs .
Dozens of police cars surrounded the prison in Bedfordshire as the riot continued inside Credit: GEOFF ROBINSON PHOTOGRAPHY Ambulance services raced to the scene, with one seen entering through the prison's main gate Credit: GEOFF ROBINSON PHOTOGRAPHY Prison Officers Association chief Mike Rolfe warned last week British jails had been engulfed by a "bloodbath".
And the union's general secretary Steve Gillan said last night: "The POA has been warning about this situation of violence in our prisons - it would appear it's coming to fruition.
"I just hope there's no prisoners or indeed prison officers injured in the violence."
Shock figures released last week revealed how the number of assaults on prison guards have increased 43 per cent on last year.
Officers were attacked 5,954 times in the 12 months to June up from 4,177 the previous year.
Justice Secretary Liz Truss admitted the figures “demonstrated the serious violence” present behind bars.
Mark Day, of the Prison Reform Trust, said: “The figures reveal a hidden emergency unfolding in our prison system.
“This cannot be allowed to become the new normal.
“The Government’s forthcoming prison safety and reform plan must get to grips with a dangerously deteriorating situation.
"The lives of people who live and work in prison depend on it.”
Scores of police officers secured the area around the prison as prison services warned of severe consequences for rioters Credit: GEOFF ROBINSON PHOTOGRAPHY Fire crews were also on the scene on Sunday night as fears grew about the scale of the unrest Credit: GEOFF ROBINSON PHOTOGRAPHY HMP Bedford was first put into use in 1801 Credit: Alamy The report said the growing numbers of assaults in the last four years coincided with “major changes to the regime, operating arrangement and culture in public sector prisons”.
And it blamed the influx of “legal highs” as a major contributor to jail violence.
It went on: “For example, restructuring of the prison estate including staff reductions, which have reduced overall running costs, and an increasing awareness of gang culture and illicit psychoactive drugs in prisons.
“As well as the dangers to both physical and mental health, trading in these illicit drugs can lead to debt, violence and intimidation.”
The Bedford riot comes days after Justice Secretary Elizabeth Truss launched her white paper on prison reform, with plans to bring in 2,500 guards UK-wide.
We pay for your stories! Do you have a story for The Sun Online news team? Email us at tips @the-sun.co.uk or call 0207 782 4368