The U.S. government has detained children at several major hotel chains during the coronavirus pandemic instead of transferring them to government-funded shelters.

The data released Friday show that since March, the Trump administration has used hotels to hold at least 660 children, most unaccompanied by a parent, before expelling them to their countries of origin.

The administration says it cannot allow children to stay in the U.S. due to the coronavirus pandemic. But opponents of U.S. immigration policy contend the pandemic is being used to deny access to asylum or other protections in federal law.

Various hotel chains have been used to house children, and at least 25 hotels and motels have been used since March to detain children.

Marriott spokeswoman Connie Kim says the company last month issued a policy “making it clear that properties should decline any requests to use our hotels as detention facilities.”

The American Civil Liberties Union has filed a lawsuit challenging hotel detention. ICE declined to comment, citing pending litigation.