A law enforcement officer walks past ICE logo ahead of a press conference on Thursday, May 11, 2017, at the U.S. Immigration and Customs Enforcement headquarters in Washington, DC.

In some facilities, all inmates were strip-searched on entry despite a lack of reasonable suspicion, the report found, in violation of ICE rules . Officials also repeatedly failed to notify ICE about "alleged or proven sexual assaults," the report authors wrote. In one instance, ICE granted a waiver to a facility to allow them not to post an emergency exit plan, citing safety issues.

In a number of facilities, problems that ICE deemed "critically important" to health and safety were allowed to persist, the report said. Those charged with inspecting ICE's facilities were understaffed and overwhelmed, and facilities were tipped off about inspections before they happened, allowing them to modify their practices and pass inspections, the inspector general found.

U.S. Immigration and Customs Enforcement failed to adequately monitor hundreds of detention facilities housing more than 35,000 individuals for several years, according to a watchdog report released Friday by the inspector general of the Department of Homeland Security, ICE's parent agency.

The report comes amid escalating criticism of ICE and its parent agency, the Department of Homeland Security. The agencies have come under fire amid President Donald Trump's push to prosecute all individuals who cross into the United States illegally. Nineteen top ICE officials sent a letter to Homeland Security Secretary Kirstjen Nielsen last week saying the politicization of immigration enforcement made it difficult for them to perform their duties.

The Department of Homeland Security reviewed inspections conducted by ICE's Office of Detention Oversight as well as a private contractor, The Nakamato Group. Nakamoto, a private firm based in Maryland, is charged with inspecting more than 100 facilities, while ODO oversees about 30.

According to the inspector general, ICE employees said that Nakamoto's inspections were "useless" and "very, very, very difficult to fail." Nakamoto inspectors "breeze by the standards" and do not "have the time to see if the [facility] is actually implementing the policies," the employees said.

In some cases, Nakamoto employees misled investigators who were looking into Nakamoto's inspection practices, according to the report.

In a statement, ICE said that it appreciated the inspector general's "positive recognition" and said it agreed with the five recommendations outlined in the inspector general report.

"ICE utilizes a layered approach to monitor detention conditions at facilities, with processes in place to implement corrective actions in instances where non-compliance to ICE detention standards is found," ICE said. "ICE will continue to ensure its detention facilities comply with relevant policies and standards through an aggressive inspections program."

In general, the report found that inspections conducted by ICE's ODO were more thorough than those conducted by Nakamoto, the private contractor.

The report found no evidence that ICE performed any quality assurance visits with Nakamoto in the past four years, despite ICE's claims that the visits occurred two to three times a year. Officials told the watchdog that ICE lacked the "right tools" to evaluate Nakamoto's performance.

Mark Saunders, Nakamoto's vice president, said he was aware of the watchdog report but declined to comment.

ICE has been contracting with Nakamoto since 2007. It most recently re-awarded Nakamoto its inspection contract in 2016, according to the report.

Nakamoto's other clients include a number of government agencies, including the Department of Justice, the Department of Health and Human Services and the Department of Commerce, according to its website.

Nakamoto's website says the company provides services such as drafting emergency plans for correctional facilities, reviewing staffing, conducting staff analysis, and ensuring compliance. Nakamoto also provides conference planning services, according to its website, and offers services such as photography, transcribing, and writing thank you letters.

Department of Homeland Security staff working on the watchdog report observed Nakamoto inspections at facilities in Georgia and Texas for a period of six months between April and August of last year, the inspector general wrote.