NEW YORK — The heat at a troubled Brooklyn jail started to fail as early as mid-January, weeks before the problem erupted into a public crisis, staff members and current and former inmates testified Tuesday at a hearing on the deteriorating conditions.

The hearing, before Judge Analisa Torres of U.S. District Court in Manhattan, followed complaints that inmates at the jail, the Metropolitan Detention Center, were being housed in intolerable conditions.

They were forced to huddle under blankets in frigid cells, lawyers said, after an electrical fire on Jan. 27 plunged much of the building into darkness. It led the jail to cancel lawyer and family visits for a week.

The heating problems were unrelated to the electrical issues but worsened just as the city experienced temperatures that were among the coldest of the winter.

Reports of the conditions drew crowds of protesters and a phalanx of elected officials to the jail over the weekend. Hugh J. Hurwitz, the acting director of the federal Bureau of Prisons, toured the jail Monday. Power and heat now have been restored and family visits have also resumed, officials said.

After the hearing, Torres took the unusual step of visiting the MDC, which sits on the Brooklyn waterfront in Sunset Park, for more than two hours to carry out her own inspection. Afterward, she rejected a request, raised by lawyers for two inmates, that she appoint a neutral observer to investigate jail conditions and report to the judge.

The judge noted that the federal public defender’s office in New York City had already made the same request in a civil suit filed against the Bureau of Prisons on Monday in Brooklyn, and she said that court should take up the issue.

The conditions at the jail also prompted defense lawyers to file emergency bail requests in Brooklyn federal court. Judge Nicholas G. Garaufis, who heard three bail cases, condemned the conditions in the jail.

“I can’t imagine people in the dark, in subfreezing temperatures, without any understanding of when it will end. It’s not humane,” Garaufis said during the proceedings.

“They’re keeping it together with Scotch tape,” Garaufis said, comparing the jail to an old, patched-up car. For years, he said, the facility’s physical state had been deteriorating, and the jail’s disrepair was exacerbated by a perfect storm of the federal government shutdown, equipment failures and a fire that knocked out the electrical grid.

The hearing before Torres in Manhattan offered some of the first public accounts by jail employees and inmates about the problems at the facility, which federal public defenders in New York have called a “humanitarian crisis.”

Anthony Sanon, the leader of the local chapter of the correction officers union, testified that problems with the heat began as early as mid-January, and another employee, John Maffeo, a facility manager, placed the date at about a week or two before the Jan. 27 fire. A third employee, Hai June Bencebi, remembered it became “extremely cold” in the jail about two days before Martin Luther King’s Birthday, when temperatures in New York were plummeting.

Current and former inmates testified that the cold and darkness of last week made living conditions almost unbearable.

Miguel Cruz, who was recently released from the jail and is awaiting trial, said he slept “completely dressed” and wearing two pairs of socks. His cellmate, he said, used book covers to try to block cold air blowing through vents into their cell. There was no hot water, he said, so he did not shower.

“It was horrible,” Cruz testified. “I wasn’t going to take a shower with frozen water.”

The jail houses more than 1,600 federal inmates who are being prosecuted in Brooklyn and, in some cases, Manhattan. Most of the detainees are awaiting trial and have not been found guilty of a crime. Torres held the hearing in Manhattan after a lawyer for a defendant, Jose Segura-Genao, complained that his client was living with limited heat and light in the jail, and, because he had no money in his commissary account, could not buy thermal undershirts and underwear.

“The last time I visited Mr. Segura-Genao, he was not wearing socks,” the lawyer, Ezra Spilke, wrote.

At one point in the hearing, Torres asked another witness, Deirdre von Dornum, who leads the federal defenders’ Brooklyn office and who has toured the jail, what a court could do to address the jail’s problems.

“I think to me the biggest problem,” von Dornum said, “is the lack of transparency.”

She suggested that a court could appoint a neutral observer who could enter the jail at any hour without warning, and also provide reports to a judge.

The U.S. attorney’s office in Manhattan, which represented the government at the hearing before Torres, declined to comment Tuesday night. The office had asked that the judge delay the hearing, telling her in a letter that the living conditions at the jail were “evolving and continue to require intensive work by MDC personnel.” The judge denied the government’s request.

Among those in attendance at the packed hearing was Geoffrey S. Berman, the U.S. attorney for the Southern District of New York.

During the hearing, Sanon, the correctional officer and president of the officers’ union chapter, testified about a power blackout at the MDC in January, two weeks before the fire, which sent almost the entire building into darkness.

“I saw the institution pretty much in the dark,” Sanon said. The poor visibility created “a dangerous situation” inside the jail, he said, and complicated tasks such as searching inmates for contraband or moving them back to their cells in a lockdown.

He said there were also problems with cold that he reported to his superiors in mid-January as corrections officers were wearing scarves, coats and hats on duty.

“Numerous COs, — I would say all of the COs — called and complained that it was freezing in the building,” Sanon testified.

Family members of prisoners were among the spectators in the courtroom and in two overflow areas that showed the proceedings on a live monitor.

Clara Salazar, 27, who sat in one of the overflow rooms, said that her father — whom she declined to name out of concern for his privacy — is an inmate at the MDC, and that the last time she said she saw him there was from the street. She was with protesters and he was inside, banging on a window alongside other inmates in a loud, clattering protest against conditions at the jail.

“We didn’t get to talk to him for a very long time,” Salazar said. “No phone calls, no emails.”

This article originally appeared in The New York Times.