WASHINGTON — Senators from both parties are demanding answers from the Trump administration about how many ISIS detainees have escaped from Kurdish-run detention centers in Syria after the president cleared the way for Turkish military action in the region.

In a letter Tuesday to Director of National Intelligence Joseph Maguire, Sens. Mark Warner of Virginia, the ranking Democrat on the Senate Intelligence Committee, and Susan Collins of Maine, a Republican on the committee, said they had "grave concern" that "numerous Islamic State detainees from detention facilities that had been run by America's Kurdish partners in the Syrian Defense Forces" had escaped.

The largely Kurdish Syrian force, known as the SDF, had been holding more than 10,000 captured ISIS fighters, including 2,000 "foreign fighters," committed jihadists who traveled from Europe, the Middle East and elsewhere to join ISIS, the senators noted.

Click here to read the letter.

"Many of these individuals are hard-core terrorists, with the kinds of expertise — bomb-making, leadership and propaganda — that had made ISIS such a threat to the United States and our allies."

After President Donald Trump cleared the way for Turkish military action against the Kurds, Kurdish officials told NBC News that staffing the detention camps would no longer be a top priority.

Warner and Collins referred to a report in Defense One, a website that covers military matters, that senior U.S. officials have "no real idea" how many fighters may have already escaped, and how many more are likely to do so.

The Office of the Director of National Intelligence, the National Counterterrorism Center and the Pentagon had no immediate comment.

A Pentagon official who requested anonymity said that by the military's count, about 100 detainees have escaped. The official did not elaborate.

"If the past is any indication, it was escaped al Qaeda in Iraq prisoners that formed the core of what became known as ISIS, contributing to the group's eventual takeover of Mosul and much of northern Iraq," Warner and Collins wrote. "The subsequent influx of foreign fighters into Iraq and Syria increased the terrorist threat to the United States and Europe. If left unchecked, the escape of ISIS detainees in Syria could lead to similar counterterrorism setbacks."

They asked Maguire to provide the Senate Intelligence Committee by Nov. 19 with "an assessment of the impact the escape of ISIS detainees in SDF custody could have on the security of United States and our allies, including the detainees who have escaped and those still residing in SDF custody."