MAZON, Ill. — Four people were transported to Morris Hospital Monday morning after a Gardner Fire District ambulance rear-ended a semi in Mazon.

According to Grundy County Sheriff's Department Chief Deputy Kevin Callahan, at about 7:30 a.m., the sheriff's department received a report of an accident involving a semi and a Gardner ambulance in the northbound lane of Illinois 47, near the railroad crossing.

Callahan said that, at the time of the crash, a train was at the crossing and the gate arms were down, with lights flashing, and there was a heavy fog that limited visibility.