Three South Florida congresswomen are calling for an investigation into the company that operates the nation's largest facility for unaccompanied migrant children, in Homestead, Florida. The shelter can hold as many as 3,200 children.

Democratic Representatives Donna Shalala, Debbie Wasserman Schultz and Debbie Mucarsel-Powell asked in the letter sent Tuesday for the inspector general of the U.S. Health and Human Services Department (HHS) to investigate a recent no-bid contract given to the shelter operator, Comprehensive Health Services.

News of the contract, worth up to $341 million, was first reported by the Miami Herald in a story cited by the congresswomen in their letter to the inspector general.

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"As representatives of Miami-Dade County, where the shelter is located, we are deeply concerned with the conditions surrounding the contracting, particularly as this for-profit company continues to financially benefit from the prolonged detention of children," they wrote.

The congresswomen note in their letter that they were denied access when they tried to visit the facility in April, "and our constitutional oversight duties continue to be impeded by the facility and the Department of Health and Human Services."

That same week, former White House chief of staff John Kelly was granted access to the facility. CBS News revealed on May 3 that Kelly had taken a job as a member of the board of directors of Comprehensive Health Services' parent company, Caliburn International.

Caliburn and HHS did not immediately reply to requests for comment.

That Kelly's visit was approved and the congresswomen's was rejected could be a cause for concern, according to Virginia Canter, chief ethics counsel for the nonprofit Citizens for Responsibility and Ethics in Washington (CREW).

Canter said in a May 9 interview with CBS News that there are strict laws governing former senior White House staff, including a clause barring former staff from exerting influence on decisions made by government employees, including those as seemingly insignificant as access to facilities.

"Any request to visit the facility needs to be cleared by the government, and the fact that you have three members of Congress who were denied access shows you that this is not something that is easily obtainable," Canter said. CREW has filed two Freedom of Information Act requests to the federal government seeking information about Kelly's role in policy decisions leading to lengthened stays for unaccompanied children, as well as how he sought access for his April visit to Homestead.

While Kelly was White House chief of staff, the administration began a crackdown on immigration that led to a dramatic increase in the length of stay of unaccompanied minors. During that time, Comprehensive's operation expanded by more than 300 percent.

One change has been repeatedly cited by HHS personnel as having increased the average length of stay for an unaccompanied migrant child in U.S. custody. In June 2018, the government began requiring fingerprint background checks of all household members of a relative seeking to sponsor a child in U.S. custody. Prior to that time, only the sponsor was required to be fingerprinted. The policy was abandoned in December, and HHS officials have since said they did not believe it added value to their system of safety checks for sponsors.

Kelly left the Trump administration at the end of that month. The congresswomen say in their letter that they also want the inspector general to investigate any decisions Kelly might have been involved with that could have led to that increase.

"We find it troubling that General Kelly's tenure in the administration led to a dramatic increase in both the number of children held at the Homestead facility and the duration of time that unaccompanied children are being kept in government custody," the congresswomen wrote.

The congresswomen also criticized the level of care provided at the facility, which they say they witnessed during previous visits when their access was approved.

"The conditions we observed during our initial visits were unacceptable, even for a temporary detention facility," they wrote.