A pair of Democratic lawmakers demanded Thursday that the company operating the nation's largest unaccompanied migrant children's shelter explain how it came to hire former White House Chief of Staff John Kelly.

Massachusetts Sen. Elizabeth Warren and Washington Rep. Pramila Jayapal sent a series of questions to the CEO of Caliburn International "in order to help inform (anti-corruption legislation) and better understand how General Kelly was appointed to the board of your company."

The letter repeatedly cites a May 3 CBS News report that revealed John Kelly's position with the company, which operates a massive government-funded shelter in Homestead, Florida, as well as three others in Texas. The lawmakers, who said in a press release that they intend to investigate Kelly and Caliburn, set a June 20 deadline for responses to their questions.

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News of Kelly's position at Caliburn ignited widespread recriminations among Democrats. In another letter to the company, on May 3, Warren accused it of profiting off White House policies that led during Kelly's tenure to a spike in the amount of time children were kept in government custody.

Caliburn did not reply to a request for comment.

"General Kelly ... was at the center of the inhumane and poorly planned immigration policies that put children in cages while separating thousands of families and that benefitted your company," the lawmakers wrote in their letter. "In fact, those policies helped a subsidiary of your company, which operates the 'nation's largest facility for unaccompanied migrant children' rake in hundreds of millions of dollars in government contracts."

The letter to Caliburn CEO Jim Van Dusen cites Kelly's role in the White House during the short-lived "zero-tolerance" policy that led to the separation of thousands of migrant children from their parents.

Kelly was also in the White House when another policy leading to longer detainments of children was implemented. 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 officials with the U.S. Department of Health and Human Services have since said they did not believe it added value to their system of safety checks for sponsors.

"General Kelly's role in promoting and helping execute these cruel immigration policies remains a stain on his decades of public service," the lawmakers wrote. "It is outrageous that he now appears to be cashing in on those same policies, as a board member for the company that benefitted from his actions as a government official."

Warren and Jayapal note in their letter that they are sponsors of ethics legislation proposed in November 2018. The Anti-Corruption and Public Integrity Act "would make it illegal for Calibum or any DHS contractor to pay General Kelly or any other former senior DHS official a dime for at least four years after they leave office," the pair wrote in their letter.

The Homestead shelter housed 2,300 children as of May 31, with a capacity of 3,200. Combined, the four shelters operated by Caliburn subsidiary Comprehensive Health Services can currently house more than a quarter of the more than 13,000 unaccompanied migrant children in government custody nationwide.

Before joining the White House in January 2017, Kelly was on the board of an investment firm called DC Capital Partners. The firm purchased Comprehensive Health Services — which at the time operated just one shelter, at a fraction of its current capacity — in 2018 and combined it with three other companies to form Caliburn. In the year since, it has dramatically expanded its unaccompanied children program while receiving federal contracts worth more than $500 million.

During that time, the Homestead operation has faced sustained criticism. On Tuesday, three Democratic Florida Congresswomen demanded its closure. They cited a recent legal filing that included testimonials from 76 children housed in the Homestead facility.

Some of the children said they had been kept at the facility for months. Many said they were led to believe that breaking small rules — taking a long shower or hugging a sibling in violation of the facility's no touching policy — might hurt their chances of living with family again.

Read the lawmakers' questions to Caliburn below, and their full letter here.

1. When did Calibum International, DC Capital, or CHSi begin discussions or negotiations with General Kelly about his appointment to the Board of Caliburn or other related entities?

a. Please provide a detailed timeline of all discussions and negotiations.

b. Are you aware of any discussions General Kelly had with DHS or White House ethics officials about his appointment or the negotiations and discussions that preceded his appointment?

c. Are you aware if DHS or White House ethics officials made any ethics determinations regarding General Kelly's appointment to the Board of Calibum International? If so, please provide copies of any documents including, determinations, ethics guidance, or ethics advice in your possession.

2. Did Caliburn International, DC Capital Partners or CHSi officials, employees or representatives discuss ethics laws and rules in relation to General Kelly's role as a board Member of Calibum International?

a. If so, please provide copies of all memoranda, notes or other materials discussing this issue.

3. Please provide detailed information of General Kelly's compensation package for serving as a board member of Caliburn International.

4. How much revenue did Caliburn International, DC Capital Partners, CHSi, or other related entities generate from operating shelters for unaccompanied migrant children in each of the last five years? Please provide annual revenues for each facility you operate for each year.

5. Please provide copies of all email or other communications between General Kelly or any associates of General Kelly and Calibum International, CHSi, DC Capital Partners, or Homestead Jobs Corps facility employees or representatives involving General Kelly's offer and decision to join the Board of Caliburn.