Human-rights attorneys in Chicago say they cannot account for more than 3,000 people arrested during a federal immigration crackdown known as “Operation Midway Blitz,” raising concerns about due process, transparency, and possible coerced departures.

Immigration and Border Patrol officers have arrested more than 3,000 people who authorities say were in the U.S. illegally and in some cases wanted for serious crimes, all in the seven weeks since feds intensified their efforts in the state.

Attorneys consulted by NBC Chicago, however, say federal authorities have refused — or are unable — to disclose where many of those detainees are being held or whether they have already been deported.

“It is quite dire,” said Mark Fleming of the National Immigrant Justice Center, which is suing federal authorities. “These are folks that have been here for decades, have long standing ties to the community, family members, employment, businesses that are all being torn apart.”