NEW YORK (CBSNewYork/AP) — The federal Bureau of Prisons said Saturday that work to restore power to a detention center in New York City where inmates have gone without heat and electricity for a week will be completed by Monday.

A tense rally was held outside the Metropolitan Detention Center in Brooklyn following news reports that hundreds of inmates there have spent the past week largely without power or the ability to communicate with their attorneys or families.

“Contractors left and will not be back until Monday, and that shows you the lack of urgency,” Congressman Jerry Nadler (D-10th) said.

Congresswoman Nydia Velazquez (D-7th) said it was “surreal” to hear the inmates banging on the federal facility’s walls to get attention.

“I am frustrated. This is America. In America, everyone has rights,” said Velazquez, whose district includes the center in Sunset Park. “It’s a violation of their human rights to be kept in the cold and not to be able to talk to anyone.”

Velazquez said she was not allowed to speak to the inmates during a Friday visit, but got access to common areas and showers. She said she and other elected officials planned to return to the facility Saturday and hoped to speak to inmates this time.

The Bureau of Prisons acknowledged in an emailed statement Saturday that the jail “experienced a partial power outage due to a fire in the switch gear room.” The bureau said a new electrical panel is being installed by an outside contractor and work is expected to be completed by Monday.

The bureau said air temperatures in the units “were within acceptable ranges” on Saturday.

Velazquez disagreed. She said lawmakers measured the temperature as low as 49 degrees in some cells. “The heat is sporadic and it’s uneven,” she said.

According to lawyers from the Federal Defenders of New York, a non profit that defends low-income people, the center has had electrical problems since the beginning of the year. Things came to a head after a fire broke out last weekend.

Lawyers for inmates at the facility, which houses people awaiting trial or awaiting sentencing on federal crimes, have said that clients with health issues are suffering in cold cells without access to warm clothes or blankets.

“Heat is a minimum standard, that is a minimum requirement for anyone that is in a correctional facility,” one demonstrator said.

In addition to heat, lawyers say the outage has knocked out power to the computers and telephones that inmates use to email their families and attorneys and to request refills of prescription medications.

Mayor Bill de Blasio said federal officials have “massively failed” the inmates at MDC.

“New York City is sending trucks with hundreds of blankets and hand warmers to the (MDC) NOW and generators are being readied for transport,” de Blasio tweeted. “We’ve told the Federal Bureau of Prisons the supplies are coming – whether they like it or not.”

The mayor later tweeted pictures from a loading dock at the facility, saying that generators were also delivered for the prisoners.

“We won’t stand by while the federal Bureau of Prisons fails them,” de Blasio said.

Attorney General Letitia James called the circumstances “unacceptable, illegal, and inhumane” in a statement sent to CBS2.

“The reported conditions at the Metropolitan Detention Center are appalling,” the statement continued. “Prisoners and detainees have rights and those rights must be enforced. My office is in touch with legal service providers and inmates’ attorneys, and closely monitoring this deeply disturbing situation.”

Some inmates have been able to talk to lawyers with the Federal Defenders on a dedicated line, but inmates represented by other lawyers haven’t been able to call them, the lawyers said.

“I need to find out what’s going on with my clients,” lawyer Ezra Spilke said Friday. “They’ve basically been incommunicado from their attorneys since the 27th, which is when the electrical fire happened.”

Officials with the American Federation of Government Employees, the union that represents corrections officers at the jail, have confirmed the lawyers’ accounts of the jail conditions.

“They’re just waiting for a disaster to happen,” jail employee Rhonda Barnwell, who works in the facility’s medical station, told reporters Friday. “There’s only heat in the afternoons since we’ve been complaining today.”

Velazquez said the heat situation seemed to be better when she visited the jail around 4 p.m. Friday but corrections officers were still wearing their coats. “There is light in the hallways but it’s not enough,” she added.

Donna Lieberman, executive director of the New York Civil Liberties Union, said in a statement, “It is shocking that the government would hold people for days on end in a dark, freezing jail during one of the coldest weeks in memory.”

A group at the rally vowed to camp outside the facility until conditions improve.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)