Conditions at five US migrant detention centres in Texas have been described as a “ticking time bomb”, as photographs emerged of people crammed in their dozens into cells far too small for the purpose.

Official investigators found thousands of people had been in Border Patrol custody for longer than the agency’s own 72-hour limit, while some had not showered for a month. Children at three of the five centres had no access to showers.

Two sites did not give child detainees hot food until inspectors arrived, and Department of Homeland Security (DHS) representatives were forced to leave one centre early because “when detainees observed us, they banged on the cell windows, shouted, pressed notes to the window with their time in custody, and gestured to evidence of their time in custody”.

One man was pictured holding a scrap of cardboard bearing the words, “Help 40 Days Here”. He was among 88 men being held in a cell designed for 41, the DHS inspector general’s office (OIG) said.

In a report on conditions at several Border Patrol sites in the Rio Grande Valley released on Tuesday, OIG added that “at one facility, some single adults were held in standing-room-only conditions for a week”. Most single adult detainees were still wearing the clothes they arrived in “days, weeks and even up to a month prior”.

'Dangerous' overcrowding of migrants in US border facilities Show all 6 1 /6 'Dangerous' overcrowding of migrants in US border facilities 'Dangerous' overcrowding of migrants in US border facilities Photos of detained migrants crowded into cells at the US border - with one holding up a sign reading simply "help" - have been released as part of a new report warning of "dangerous" overcrowding. The memo was sent to the Department of Homeland Security by its Inspector General, containing photos taken at border facilities in the Rio Grande Valley over a week in June DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Eighty-eight adult males held in a cell with a maximum capacity of 41, some signalling prolonged detention to OIG Staff on June 12 DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Overcrowding of families observed by OIG on June 11, at a border patrol facility in Weslaco, Texas DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Migrant families overcrowding a border patrol facility on June 11 in McAllen, Texas DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Fifty-one adult females held in a cell designated for male juveniles with a capacity for 40 at Border Patrol’s Fort Brown Station DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Migrant families overcrowding a border patrol facility on June 11 in McAllen, Texas DHS/OIG

And despite rules ordering Border Patrol agents to recognise people’s dietary and religious needs, “many” adults were being fed only bologna [processed sausage] sandwiches. “Some detainees on this diet were becoming constipated and required medical attention,” OIG’s report said.

Images showed children sleeping on the floor in chain-link cages with only foil blankets for comfort. Inspectors said overcrowding had become “dangerous”, quoting a senior manager at one facility as calling the situation a “ticking time bomb”, and a hazard for both staff and the people detained.

It comes just weeks after the watchdog rapped Immigrations and Customs Enforcement officials over “egregious violations” of standards at two of their facilities, where staff were found to be serving spoiled food.

Donald Trump’s administration has faced criticism for its handling of the flow of people trying to enter the US from Latin American countries. Mr Trump has called the asylum system broken, saying that some take advantage of it with frivolous claims.

The OIG report noted that the Rio Grande area of Texas had seen a 124-per-cent increase in attempted border crossings in the last year. Border Patrol facilities were holding about 8,000 people during the inspectors’ visits in June, with 3,400 detained longer than the 72 hours permitted. Of those,1,500 had been held more than 10 days.

Eight hundred and twenty-six of the 2,669 children at Border Patrol’s facilities had been held longer than the 72 hours generally permitted under the customs agency’s standards and a prior court finding.