A lawsuit brought by lawyers for inmates at a federal detention center in New York City calls a weeklong power failure that left inmates with no electricity and limited heat for a week a "humanitarian crisis."

The lawsuit, filed Monday in Brooklyn federal court by the Federal Defenders of New York, alleges that the Federal Bureau of Prisons violated the constitutional rights of about 1,600 inmates at the Metropolitan Detention Center by denying legal visits after a Jan. 27 fire caused the outage.

The lawsuit said the outage caused "inhumane" conditions for inmates and the response was "woefully inadequate." It calls for the appointment of a special master to inspect the lockup.

A tense rally was held outside the jail on Saturday 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. A group at the rally vowed to camp outside the facility until conditions improve.

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Officials say power was restored Sunday around 6:30 p.m. at the detention center in Brooklyn and staff was working to restore the facility to normal operations.

The Department of Justice said Sunday it would work with the Bureau of Prisons to probe what happened there.

Meanwhile, a bomb threat brought scores of police to the area Monday and added to the chaos. Visitors and contractors were escorted out of the jail as a precaution after the threat was called into the facility around 10:25 a.m.

Officers ordered protesters and reporters to move away from the front of the facility as a precaution. And family members who came hoping to find how loved ones were doing were turned away.

"They don't want us to see how they look as far as they could be anorexic, they could have bags under their eyes from not being able to sleep at night because it's dangerous being the dark," Shalicia Anderson, an inmate's wife, told CBS New York.

Police and the Bureau of Prisons say no devices were found and no credible threat was identified. The NYPD is investigating the source of the threat.