A "jolt" explosion shakes the city of Illinois

Four people were hospitalized after an explosion that rocked the ground and a fire broke out Friday night in an industrial complex in Lake County, Illinois.

Shortly before 10 pm The Lake County Sheriff's Department said it was working to determine the cause of an explosion in the Gurnee-Waukegan area.

"We are aware of a very strong explosion and an earthquake in the Gurnee region", the agency tweeted. "If you have direct knowledge of the incident, please call your local law enforcement."

Hours after the initial explosion, the crews continued to fight the fire and urged residents to stay away from the scene.

The explosion occurred near the border between Gurnee and Waukegan, about 35 miles north of Chicago.

Officials were looking for second-team workers likely to have stayed in the building during the blast, said the Waukegan Police Cmdr. Joe Florip told NBC Chicago.

Living conditions for those taken to the hospital had not been revealed, Waukegan fire chief Steven Lenzi told the television channel.

"Something has exploded," said Emily Laughlin, a resident of the station. "It looked like it was a building, but they kept everyone from getting closer."

Other people in the area posted photos and a video of the explosion online and described it as a "sound boom".

Some southern Wisconsin residents said they felt the blast, NBC reported.

According to the station, electricity was cut off for nearly 1,000 inhabitants and the windows were broken.