Citing unnamed "security concerns," federal authorities have placed a notorious Manhattan jail on lockdown for the past five days — barring detainees from speaking with their families, attorneys, or medical professionals.

David Patton, executive director of Federal Defenders of New York, told Gothamist that the Metropolitan Correctional Center has been inexplicably sealed to outsiders since Thursday.

"We have no access to the institution," he said. "We have no idea what the hell is going on in there."

Authorities with the federal Bureau of Prisons did not respond to inquiries from Gothamist. Jail sources told the Post on Friday that visitations had been suspended due to concerns that a gun may have been smuggled inside the facility.

"That should not be grounds for a five day total closure," Patton said. "They're supposed to have access to family, to spouses, children, and their lawyers. That's a primary mission of a pre-trial detention. To go five full days with zero access is just entirely unacceptable."

The federal jail has a population of roughly 760 people—nearly twice the number it was originally built to accommodate. The vast majority have not yet been convicted of a crime.

Detainees at MCC say they are routinely subjected to inhumane conditions, including vermin infestations, substandard medical care, violence at the hands of guards, and heating and plumbing issues. The facility faced significant scrutiny for the death of Jeffrey Epstein, who is believed to have taken his own life in custody as the guards tasked with watching him slept for hours.

"I can't possibly convey to you the amount of obfuscation and lack of transparency in that institution," said Patton. "They don't tell us a damn thing."

New York City's other pre-trail federal jail, Metropolitan Detention Center in Sunset Park, became the subject of national outcry and a Department of Justice investigation last January after detainees were deprived of heat and other necessities on one of the coldest weeks of the year.

That shutdown at MDC, which lasted five days, represents the only other time in recent memory that one of the city's pre-trial jails has been locked down for so long, Patton said.