BOSTON (AP) -- Several political leaders, including Massachusetts U.S. Sens. Edward Markey and Elizabeth Warren, attacked the leader of a troubled health care system on Thursday for refusing to comply with a subpoena to appear before a Senate committee.

Lawyers for Steward Health Care CEO Ralph de la Torre said Wednesday that he won't testify before a committee investigating the Dallas-based hospital company's bankruptcy because a federal court order prohibits him from discussing anything during an ongoing reorganization and settlement effort.

Warren and Markey both dismissed those concerns on Thursday, saying de la Torre is trying to avoid accountability.

Steward, which operated about 30 hospitals nationwide, filed for bankruptcy in May. It has been trying to sell its more than half-dozen hospitals in Massachusetts, but received inadequate bids for Carney Hospital in Boston and Nashoba Valley Medical Center in the town of Ayer, both of which closed on Saturday. A federal bankruptcy court on Wednesday approved the sale of Steward's other hospitals in Massachusetts.

In a letter Wednesday to Vermont U.S. Sen. Bernie Sanders, who chairs the Senate Health, Education, Labor and Pensions Committee, de la Torre did not rule out testifying before the committee at a later date.

"He is in hiding because he does not want to answer to the American people or Congress or the patients and workers of Massachusetts for what he has done," Markey, speaking at a press conference Thursday, said of de la Torre. "He wants to hide from the accountability of what the last five months have exposed."

Warren said de la Torre could invoke his constitutional right against self-incrimination if he "believes the answers will put him at risk for going to jail."

"Ralph de la Torre is one more rich guy who thinks the rules don't apply to him," Warren said. "He seems to think he's above the law and that he can take whatever he wants and not have to answer for any of the destruction that he leaves behind."

Warren argued that de la Torre's decision not to appear should result in his ouster from Steward.

"I understand it's way late in the process, but I'd like to see someone else who gets their eyes on all of the information that's happening confidentially, internally, and not disclosed to the public -- someone besides Ralph de la Torre," she said.

In their letter to Sanders, lawyers for de la Torre said the Senate committee is seeking to turn the hearing into "a pseudo-criminal proceeding in which they use the time, not to gather facts, but to convict Dr. de la Torre in the eyes of public opinion."

Sanders said in a statement that he will work with other members of the panel to determine the best way to press de la Torre for answers.

"Let me be clear: We will not accept this postponement. Congress will hold Dr. de la Torre accountable for his greed and for the damage he has caused to hospitals and patients throughout America," Sanders said. "This Committee intends to move forward aggressively to compel Dr. de la Torre to testify to the gross mismanagement of Steward Health Care."

The committee's options include holding de la Torre in criminal contempt, which could result in a trial and jail time; or civil contempt, which would result in fines until he appears. Both would require a Senate vote.

De la Torre also refused invitations to testify at a Boston field hearing earlier this year chaired by Markey.