A caboose in a rail yard servicing a sprawling business park caught fire Saturday night in Elk Grove Village, authorities said.
A passer-by reported the fire about 7:13 p.m. in a yard on the 2400 block of Arthur Avenue near Elmhurst Road.
When firefighters arrived about three minutes later, crews thought they were battling a blaze in a train.
"The smokes and flames were so heavily involved it was hard to see exactly what we were dealing with," Elk Grove Battalion Chief Mark Sellers said.
The fire turned out to be contained to a stand-alone caboose parked on the tracks in a yard owned by Chicago Terminal Railroad, he said.
Fire officials brought in additional companies because of the blaze's proximity to businesses in an industrial area next to O'Hare International Airport.
Nearly 30 firefighters responded, including units from Des Plaines, Itasca and Wood Dale.
While the blaze was quickly extinguished, the flames destroyed the inside of the caboose, unoccupied when crews first arrived, Sellers said.
"The inside was gutted by the fire," he said.
The Elk Grove Village Fire Department is investigating the cause. Damage estimates were not immediately available.