DETROIT (WWJ) –  Investigators say a mechanical issue may be to blame for Wednesday’s fire that destroyed a number of city buses at a Detroit Department of Transportation bus yard.

An arson investigator says the fire appears to have started underneath one bus and spread to the others.

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The two-alarm fire broke early Wednesday morning at D-DOT’s Coolidge bus yard on Schaefer, near Schoolcraft. Officials said eight buses burned, costing a total of more than $3 million.

WWJ’s City Beat Reporter Vickie Thomas reported live from the scene, where thick, black smoke was pouring out of the roof of the one-story building.

D-DOT building roof (WWJ Photo/Bill Szumanski)

Apparently, buses in the back of the building caught fire sometime around 4:30 a.m. and, because they were way in the back, it was hard for firefighters to reach them.

To make matters worse, there were several hundred gallons of fuel burning as well, causing authorities to bring in the Hazmat team.

“We had difficulty with the water supply but we have one bay, bay 5 that had approximately five buses in it. We’re not sure how the fire started but we did get a partial roof collapse which challenged us even further to get to the fire, but eventually they got the fire suppressed and contained. The fire is extinguished, we have to do an overhaul though,” said Fire Commissioner Don Austin.

“Our biggest situation was not having sufficient hydrant locations inside of the yard,” added Senior Fire Chief Michael Herron. “We were actually passing water to another apparatus from the hydrant here to get to that area back there, because there are no hydrants in that yard at all, and it goes back seven or eight blocks.”

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Herron said the building doesn’t have a sprinkler system, or at least not one that was working.

“If the sprinkler system was working and did its job, it probably would have contained the fire to prevent it from getting worse, the way it was,” Herron said.

According to Austin, one firefighter did suffer a pinched nerve from pulling a long hose, but he is expected to be OK. No other injuries were reported.

Authorities actually used D-DOT buses to block traffic in the area of Schaefer and Schoolcraft for several hours after the fire started.

A spokesperson for Detroit Mayor Dave Bing’s office told WWJ about 50 percent of D-DOT’s bus fleet is housed at the Coolidge terminal, and 50 percent of those were already on the road at the time the fire broke out.

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An investigation is ongoing.