At least nine babies are being detained by U.S. Immigration and Customs Enforcement at a Texas facility with inadequate medical care, according to a complaint filed Thursday with the federal government calling for their immediate release.

The babies — all less than a year old, with some younger than 6 months — are being held with their mothers at a detention facility in Dilley in west Texas.

The complaint, filed by immigration-rights groups, cites an “alarming increase” in the number of immigrant babies in government detention, and expresses “grave concerns” about the lack of medical services for this “vulnerable population.” Dilley is located more than an hour from the nearest metropolitan area, San Antonio, which offers medical services that would be required in the event of an emergency.

Mothers in the Dilley facility have complained that their babies’ nursing and sleep habits have changed dramatically in detention and that they are getting sick, according to the complaint. Even healthy babies require a regimen of checkups and vaccinations, which the facility is ill-equipped to provide, according to the complaint by the American Immigration Council, American Immigration Lawyers Association, and the Catholic Legal Immigration Network.

Other health concerns include long delays in receiving medical attention and a lack of follow-up treatment.

Detention poses special risks to babies because of their vulnerability to infection in close quarters. Keeping children away from a home environment can also have consequences for their development, experts say.

Physicians for Human Rights said in a statement accompanying the complaint that experts are “gravely concerned about the long-term developmental and mental health impact of detention on infants.” Even babies confined with parents suffer “damaging impact” on their physical and mental health, the group said.

ICE responded in a statement that it is “committed to ensuring the welfare of all those in the agency’s custody, including providing access to necessary and appropriate medical care.”