WASHINGTON — Government investigators have identified poor conditions in another sector of the southern border, publishing graphic photos showing extreme overcrowding in Rio Grande Valley migrant facilities and finding that children there did not have access to showers and had to sleep on concrete floors.

Investigators for the Department of Homeland Security who visited border stations in the El Paso, Texas, sector in May found similar conditions: migrants being held in temporary facilities for weeks rather than days, single adults living in standing room-only cells with no space to lie down, and concerns about serious health risks.

Overcrowding of families observed by the Department of Homeland Security Office of Inspector General on June 10, 2019, at Border Patrol's McAllen, Texas, station. OIG

The investigators for the DHS Office of the Inspector General toured five Border Patrol facilities and two ports of entry in the Rio Grande Valley sector during the week of June 10 and published their report as a "management alert" to the department on Tuesday.

Read the full report here.

The Rio Grande Valley of Texas has the highest volume of immigrants along the United States-Mexico border. At the time of the visits by investigators, Border Patrol was holding 8,000 detainees in custody, with 3,400 being held longer than the 72-hour limit.

One senior manager at a facility called the situation a "ticking time bomb," according to the report. When immigrants detained in the facilities saw investigators walking through, they banged on the cell windows and pressed notes against the plexiglass to show the length of time they had spent in custody. One said, "Help. 40 Day Here."

Eighty-eight males held in a cell with a maximum capacity of 41, some signaling prolonged detention to Department of Homeland Security Office of Inspector General staff, on June 12, 2019, at Border Patrol's Fort Brown Station. One man held up a handwritten sign that said "HELP. 40 DAY HERE". OIG

Overcrowding in a room for adult males at the Border Patrol's McAllen, Texas, facility on June 10, 2019, observed by Department of Homeland Security Office of the Inspector General staff. Faces blurred by source. Office of Inspector General

On Monday, NBC News published findings by the inspector general that detailed poor conditions for migrants in border stations in El Paso as far back as May 7. Acting DHS Secretary Kevin McAleenan said at a press conference Friday that reports of poor conditions for children in border stations were "unsubstantiated." McAleenan said children were given showers as soon as they could be made available.

"Most single adults had not had a shower in CBP custody despite several being held for as long as a month," according to the latest report on conditions in the Rio Grande Valley.

The report also detailed what it called "security incidents" in which immigrants have tried to escape and once refused to return to their cells after being removed during maintenance. To address the problem, Border Patrol called in its special operations force to "demonstrate it was prepared to use force if necessary," the report said.

Overcrowding of families observed by Department of Homeland Security Office of Inspector General on June 11, 2019, at Border Patrol's McAllen, Texas Centralized Processing Center. OIG