Authorities at Chicago Post Office
© Becky Jacobs/Post-TribuneAuthorities were on the scene Wednesday, Sept. 6, 2017, where a possible explosion occurred at the East Chicago post office.
An FBI official said investigators are working to determine "if there are any terrorism links" after an explosion at the East Chicago post office Wednesday evening, but that "there is no ongoing public safety concern."

The FBI confirmed Thursday that one pipe bomb detonated shortly after 6:30 p.m. at the Indiana post office, 901 E. Chicago Ave., FBI spokeswoman Chris Bavender said in a release.

"At this time, investigators are still trying to ascertain if there are any terrorism links," Bavender said.

One female post office employee was treated for minor injuries from the detonation, officials said. She was taken to St. Catherine Hospital in East Chicago Wednesday with injuries that were not life-threatening, East Chicago Fire Chief Anthony Serna said.

Two employees were inside the building at the time of the detonation and another was out making deliveries, an East Chicago fire official said Wednesday.

The post office was "up and running for business" Thursday morning, U.S. Postal Inspector Mary T. Johnson said.

"There is no disruption of mail delivery service," Johnson said.

The explosion caused "no damage" inside the post office, Johnson said.

The FBI continued to investigate the incident Thursday, and "investigators are working to determine a motive and identify the perpetrator(s)," Bavender said.

Bavender asked anyone with information about the Wednesday incident to call 800-225-5324 or visit fbi.gov/tips.

Richard Ligon, a former U.S. Postal Service inspector, said that incidents such as what happened in East Chicago are, luckily, rare in Northwest Indiana.

Before retiring in 2004, Ligon, of Gary, said he worked as a team leader and supervisor for the U.S. Postal Inspection Service in northern Indiana. Part of his job included training postal employees and area businesses about signs to look for in identifying suspicious packages. Those could include a wire hanging out, a ticking sound, a vibrating package, grease or oil stains, or the smell of gunpowder, he said.

If anything seems off with an item in the mail and there's no return address, "don't take a chance," Ligon said.

The FBI said Thursday that people should "immediately call 911 if they receive a suspicious package or mailing," as well call their local FBI office and the U.S. Postal Inspection Service at 877-876-2455.

"You can't be too cautious when it comes to improvised explosive devices and bombs," Ligon said.

The FBI did not specify if the pipe bomb was included in a package or where it was located in the building. But Ligon said that pipe bombs can be dangerous and unpredictable, depending on if it is connected to a timed device.

"Anybody that survives a pipe bomb, it's a blessing," Ligon said.

If a suspected bomb is found, inspectors usually call in bomb teams, Ligon said. In East Chicago, the Porter County Sheriff's Department provided its bomb team and truck, Sheriff David Reynolds said. The Lake County Sheriff's Department also provided police dogs, spokesman Mark Back said.

Multiple agencies were called to the scene Wednesday evening, staying into the night, including East Chicago police and fire, Hammond police, federal Bureau of Alcohol, Tobacco, Firearms and Explosives agents, and Indiana State Police.

Emergency crews blocked off a stretch of Chicago Avenue on Wednesday evening from the railroad tracks at Huish Drive a couple of blocks west to Melville Avenue.

The FBI did not release additional information Thursday.