Lockland - A massive fire at the former Stearns & Foster mattress factory sent smoke billowing across Interstate 75 Saturday morning and required crews and equipment from at least 24 local fire departments to combat.

The four-alarm fire, which started at about 9 a.m. in the 200 block of Shepard Avenue, was still burning eight hours later. The smoke plume was visible for miles.

The huge complex, which spans Shepard Avenue, includes more than 1.2 million square feet. The fire occurred in an empty warehouse portion on the east side of Shepard Avenue.

No one appeared to be inside the area that caught fire and no major injuries have been reported, fire officials said. But some apartments along nearby Wyoming Avenue were evacuated as a precaution.

Eight firefighters have been treated for heat exhaustion.

The fire backed up traffic on I-75, which was reduced to one lane northbound. It also delayed traffic flowing west from I-74 onto I-75.

One reason the fire has burned so long: small underground water mains aren't providing enough pressure for all the firefighters' hoses, fire officials said. Another problem: a train ran over eight sections of fire hose laid by the Reading Fire Department.

Crews were inside the building fighting the fire when they lost water pressure. Two minutes after moving back to safer positions, a wall collapsed where firefighters were originally standing.

"(Losing water pressure) is a pretty bad situation. The only thing worse would be to have a collapse, which we also had," said Wyoming Fire Chief Robert Rielage.

The complex, parts of which were built in 1840, is so large it spans Shepard Avenue. So far, the fire is limited to the east side of the street.

The complex had its own water supply and fire suppression system, but the system was shut down after the auction, said Bill Welshans, Lockland fire chief.

Adding to the complications: cotton dust from decades of mattress-making helped fuel the flames. And holes left in floors where machinery was removed made moving around dangerous for fire fighters.

"This building going up was pretty much our worst fear and it became reality," Rielage said.

Having a train cut some hoses didn't help, either. Fire officials said they notified CSX to stop its trains about a half-hour before laying hoses across the tracks.

"They obviously didn't get the message," Rielage said.

To get trains rolling again, crews dug holes under the tracks to allow hoses to cross.