The Department of Homeland Security is expanding its efforts to identify Americans who oppose Immigration and Customs Enforcement by sending tech companies legal requests for the names, email addresses, telephone numbers and other identifying data behind social media accounts that track or criticize the agency.

In recent months, Google, Reddit, Discord and Meta, which owns Facebook and Instagram, have received hundreds of administrative subpoenas from DHS, according to four government officials and tech employees privy to the requests. They spoke on the condition of anonymity because they were not authorized to speak publicly.

Google, Meta and Reddit complied with some of the requests, the government officials said. In the subpoenas, the department asked the companies for identifying details of accounts that do not have a real person’s name attached and that have criticized ICE or pointed to the locations of ICE agents. The New York Times saw two subpoenas that were sent to Meta over the past six months.

The tech companies, which can choose whether or not to provide the information, have said they review government requests before complying. Some of the companies notified the people whom the government had requested data on and gave them 10 to 14 days to fight the subpoena in court.