On the 10th floor of a federal building in Lower Manhattan, there is a holding area where immigration authorities have typically held a few dozen immigrants at a time for a few hours before transferring them to detention centers.

But as the Trump administration expands its immigration crackdown, the space has become overcrowded and people sleep sprawled on the floor, sometimes for days, according to those who have spent time there.

Descriptions of the conditions at the center, the New York City field office of Immigration and Customs Enforcement, have prompted several congressional Democrats to demand that they be allowed inside for oversight purposes. Those demands have been denied.

On Friday, seven New York City Democrats plan to escalate their efforts to get onto the 10th floor by sending a letter to Kristi Noem, secretary of the Department of Homeland Security, which includes the immigration agency, known as ICE. In the letter, they accuse the immigration authorities of violating federal laws that allow members of Congress to tour facilities where migrants are being held.

From New Jersey to California, ICE premises have turned into political battlegrounds over President Trump’s immigration agenda, leading to the arrests of several Democratic officials.

“Congressional oversight is essential to bring transparency to the conduct of the Department of Homeland Security,” the lawmakers say in the letter. “Given the overaggressive and excessive force used to handcuff and detain elected officials in public, DHS’s refusal to allow members of Congress to observe the conditions for immigrants behind closed doors begs the obvious question: what are you hiding?”