WASHINGTON (AP) — Democratic lawmakers are raising questions about the federal Bureau of Prisons' release of high-profile inmates and are calling for widespread testing of federal inmates as the number of coronavirus cases has exploded in the federal prison system.

Sen. Kamala Harris and Rep. Hakeem Jeffries sent a letter Monday to Attorney General William Barr and Bureau of Prisons Director Michael Carvajal over the home confinement policies. They expressed concern that a number of high-profile inmates, including former Trump campaign chairman Paul Manafort and former Trump lawyer and fixer Michael Cohen, had been released despite not meeting all the criteria that the agency has set for inmates prioritized for home confinement.

"As President Trump's associates are cleared for transfer, tens of thousands of low-risk, vulnerable individuals are serving their time in highly infected prisons," the lawmakers wrote.

They pointed to the case of Andrea Circle Bear, a 30-year-old pregnant inmate whose baby was delivered by cesarean section while she was on a ventilator after being hospitalized with coronavirus symptoms and who died in federal custody in late April. They also pointed to the case of a 67-year-old man serving a sentence at FCI La Tuna, a low-security prison in Texas, who has advanced coronary disease and who was initially told he would be released to home confinement but later was told it was rescinded because he hadn't served at least half of his sentence.

Prison advocates and congressional leaders have been pressing the Justice Department for weeks to release at-risk inmates ahead of a potential outbreak, arguing that the public health guidance to stay 6 feet (1.8 meters) away from other people is nearly impossible behind bars. And they've raised alarm about what they've described as mixed messages from the prison agency about the criteria for who can be released.

Barr ordered the Bureau of Prisons in March and April to increase the use of home confinement and expedite the release of eligible high-risk inmates, beginning at three prisons identified as coronavirus hot spots.

Under the bureau's guidelines, priority is supposed to be given to those inmates who have served half of their sentence or inmates with 18 months or less left and who served at least 25% of their time. The bureau has discretion about who can be released -- and used it in Manafort and Cohen's cases.

"These examples make clear that there are two systems of justice in our country — one for President Trump and his associates, and another for everyone else," Harris and Jeffries wrote.

The Bureau of Prisons has disputed that it is giving any preferential treatment to high-profile inmates and has said it has placed 3,544 inmates on home confinement since Barr first issued a memo ordering an increase in the use of home confinement in late March.

The response from the Bureau of Prisons on the coronavirus has raised alarm among advocates and lawmakers about whether the agency is doing enough to ensure the safety of the about 137,000 inmates serving time in federal facilities.

As of Monday, 5,234 inmates had tested positive for COVID-19 since late March; the Bureau of Prisons said 3,605 had recovered. At least 64 inmates have died.

And even though officials have stressed infection and death rates inside prisons are lower compared with outside, a high number of inmates tested come back positive — signs that COVID-19 cases are left uncovered.

Separately, Sens. Elizabeth Warren and Cory Booker asked the Bureau of Prisons to immediately begin conducting "universal diagnostic testing" for all federal inmates and staff members, including those held at privately run facilities, and to publicly release daily data on the number of inmates and staff members who have been tested.

"Widespread and continued diagnostic testing is crucial to controlling the COVID-19 pandemic," they wrote.

The lawmakers said the Bureau of Prisons has "not been forthcoming with specific testing protocols" and is not providing specific information about the testing capacity at federal prisons across the U.S.

The Bureau of Prisons has said it has ramped up its testing capabilities and has deployed more than 30 testing machines at different coronavirus hot spot prisons and quarantine sites across the nation. Inmate testing at the designated sites is being performed using Abbott's ID Now point-of-care test technology, which the Food and Drug Administration has flagged for potentially returning false negative results. A study by New York University showed that the device returned false negatives for 48% of tests that were found to be positive using another testing technology.

In a statement, Abbott said the NYU study results were inconsistent with other studies, which have shown performance rates ranging from more than 80% to as high as 94%.

Testing is not available for employees at federal prison facilities, the agency has told staff members, and wardens are encouraged to provide a list of possible testing sites in the community where staff can be tested.