EAST CHICAGO, Ind. (AP) — A postal worker was injured when a pipe bomb exploded at a post office in northwestern Indiana, and the FBI said Thursday it is investigating whether it was an act of terrorism.

The investigation into the explosion shortly after 6:30 p.m. Wednesday at the facility in East Chicago “remains open and active,” the agency said in a statement, urging the public to come forward with tips.

“Investigators are working to determine a motive” and who was responsible, the FBI said in a statement Thursday afternoon. “At this time, there is no ongoing public safety concern.”

The FBI said in an earlier statement it was “still trying to ascertain if there are any terrorism links” to the blast. FBI spokeswoman Christine Bavender said Thursday afternoon that terrorism has not been ruled out.

A postal employee was treated for minor injuries, the FBI said.

Bavender said the public is encouraged to contact the agency with any information on the explosion.

Meanwhile, the post office about 20 miles (30 kilometers) southeast of Chicago reopened for business Thursday, Postal Inspector Mary T. Johnson said. The office sustained no damage, Johnson said.

Local law enforcement also assisted in the investigation. Porter County’s bomb squad responded with a bomb disposal robot. Police dogs from the Lake County Sheriff’s Department were at the scene.

A roadway near the post office was blocked off as authorities investigated.

FBI contacts: 1-800-225-5324 and

Tips for FBI: 1-800-225-5324 or