A DOJ official sent a letter to Senator Dick Durbin and Congressman Don Manzullo saying it is committed to acquiring the facility later this year.
Once the property has been acquired, the entire space will be made available to the Federal Bureau of Prisons.
President Barack Obama has eyed Thomson as a potential site for detainees held at the U.S. prison at Guantanamo Bay, Cuba, but he's facing strong resistance in Congress.
