Three members of Massachusetts’ congressional delegation are questioning the Trump administration’s decision to divert immigration officers from Northeast offices to assist with processing asylum cases at the southern border, leaving behind a backlog of 40,000 New England cases.

In a letter to acting US Citizenship and Immigration Services director Ken Cuccinelli, Senators Elizabeth Warren, Senator Edward J. Markey, and Representative Ayanna Pressley called the move an “unfair and unjustified shift of resources” and demanded written answers to a series of questions about the operations of the affected office in Boston.

“This appears to be another cruel and unnecessary action by the Trump Administration to hurt immigrants,” the lawmakers wrote.

USCIS told attorneys earlier this month in an e-mail, which the Globe obtained, that it would no longer schedule any new asylum interviews in Boston and only a “small number” in Newark, because of “shifting priorities and the continued influx of cases at the Southwest Border.” Staff will finish cases in which interviews already took place, the letter said.

The types of cases that are being affected in New England are called “affirmative” asylum cases. The vast majority of affirmative asylum-seekers arrived legally, according to immigration advocate and lawyer Matt Cameron, and apply for asylum within a year. Asylum officers then interview the applicants and determine if their claims are valid. In March, the Boston office completed almost 200 cases, approving asylum for 34.

The diversion of staff means thousands of asylum seekers are being left in limbo. In their letter, Warren, Markey, and Pressley press Cuccinelli on how much longer those in line for asylum interviews should expect to wait.

“When does the USCIS plan to lift the suspension on scheduling new asylum interviews in the Boston Asylum Sub-Office?” one of the questions reads.

Senator Jeff Merkley first shed light on the diversion of staff last week, sparking an outcry among Democrats and immigration advocates.

Cuccinelli soon pushed back in his own tweet, calling the allegation “false,” but Merkley pointed to the e-mail announcing the halt of interviews as evidence of his claim.