Rebecca Clark with the Illinois Emergency Management Agency said the agency is investigating with state and local partners, but she had no other information. She said she heard what she called a "loud boom" from her office in Springfield.
"It was just a loud boom, an audible boom that I heard. I didn't feel anything — it was just a sound," she said.
Clark said state and local agencies were checking to make sure their critical infrastructure was fine.
Decatur Fire Department’s Deputy Chief Dan Kline told the Herald & Review that a booming noise was heard about 11:28 a.m. CST, prompting concerned calls to Decatur’s police and fire departments.
"I went up on the roof of Station One after we heard it and looked around but didn’t see any smoke or anything," Kline said. He said the noise was so loud that he thought "someone had dropped something heavy upstairs" in the fire department building.
Springfield Police Lt. Jason Brands said officers received numerous reports from residents who heard a loud noise, and that other local communities received the same type of reports from the public.
"We have no idea it was. There have been absolutely no reports of anything actually damaged. It's just that everyone has been calling saying they heard an explosion," Brands said, adding that there was speculation it was "something in the atmosphere."