Employees and patrons inside a Fairview Heights restaurant called the fire department about 11:30 p.m. Wednesday after seeing smoke come out of electrical outlets in the wall.
Deputy Fire Chief Bruce Green said it appeared a cigarette butt was thrown in some mulch near the TGI Fridays building and smoldered until it found an opening in the restaurant's wall, according to a KMOV report.
Green told KMOV it was a "freak accident" and noted crews did not know when the cigarette was tossed into the mulch.
The restaurant, in the 6900 block of North Illinois Street, was damaged near the entrance as crews tore out some wall to stop the smoldering from spreading, a KDSK report stated.
Fox 2 Now reported the everyone was evacuated from the building and there was no information available on whether anyone was injured.
KMOV said Green thought the restaurant may reopen later Thursday.