Federal lawmakers, including several Massachusetts Democrats, are probing a Trump administration policy change that has some severely ill immigrants facing deportation.

In a Friday letter to a trio of administration officials, the lawmakers said that last month applicants for “medical deferred action” started to receive notices from US Citizenship and Immigration Services “rejecting their request for deportation referral and notified them that they have 33 days to depart the country or risk deportation.”

The notices stated that the agency’s field offices no longer consider such requests. Such deferred action provides temporary relief from deportation for “immigrants, and their families, with life-threatening health conditions that cannot be properly treated if they were deported,” according to Representative Ayanna Pressley’s office. Pressley is among those who signed the letter.

According to the letter, the agency’s rejections have spawned confusion, and lawmakers now want authorities to provide data detailing deferred action requests and documentation that detail current policies.

According to lawmakers, USCIS has said that US Immigration and Customs Enforcement is now considering the requests, but ICE told US Senator Edward J. Markey’s staff that it does not and will not consider such requests until an individual has been through removal proceedings and has an order for removal. Markey and Senator Elizabeth Warren also signed Friday’s letter.

The policy change came as a surprise to patients, caregivers, lawmakers, and some federal officials, with no formal announcement. Immigration advocates are calling the new policy cruel and inhumane. People requesting deferred actions do so because of severe medical conditions like cancer, epilepsy, cerebral palsy, muscular dystrophy, and cystic fibrosis, according to the letter.

In the past, medical deferred action has been a form of prosecutorial discretion that has allowed immigrants with major illnesses, and their families, to remain in the United States, work legally, and be safe from deportation while receiving treatment, lawmakers said in the letter. USCIS receives about 1,000 deferred action requests annually. Immigration lawyers estimate that at least 40 families in the state could be affected by the change in policy.

“Individuals requesting deferred action from USCIS are among the most vulnerable,” lawmakers said in the letter.

The letter was addressed to acting Homeland Security Secretary Kevin McAleenan; Ken Cuccinelli, acting director of USCIS; and Matthew T. Albence, acting director for ICE.

The letter asks officials to provide data regarding medical deferred action requests, to articulate current policies, and to explain the rationale for the policy change, among other questions.