EAST CHICAGO, Ind. (AP) — The FBI says there’s no ongoing public safety concern from a pipe bomb explosion that injured an employee at a northwestern Indiana post office, and a postal inspector says the site has reopened for business.

The FBI also said in a statement Thursday afternoon that investigators are working to determine a motive, who was responsible and whether there’s any link to terrorism. The agency says there was a single pipe bomb.

It says a one postal employee was treated for minor injuries.

Postal Inspector Mary T. Johnson says the post office about 20 miles (30 kilometers) southeast of Chicago sustained no damage inside and is open for business.