CHICAGO (AP) — Police say a federal agent has been shot and critically wounded in Chicago while working on an investigation with local authorities.

Chicago police spokesman Anthony Guglielmi (goo-lee-EHL'-mee) says in a tweet that the Bureau of Alcohol, Tobacco, Firearms and Explosives agent was working with Chicago officers at the time of the shooting about 3:15 a.m. Friday on the city's South Side.

Guglielmi federal authorities will release additional information. The Associated Press has sent an email seeking comment from an ATF spokeswoman in Chicago.

No arrests have been reported.

Luz Campos, who lives near where the shooting took place, told the Chicago Tribune she was in her kitchen when she heard someone say "open the door" and then heard what she thought was the sound of fireworks.