Petaluma firefighters battled a series of small blazes along Highway 101 Tuesday night that sent heavy smoke across the road during the evening rush, snarling traffic.

It is likely the fires were the result of a vehicle spreading sparks because of some kind of mechanical problem, perhaps disintegrating breaks or a faulty catalytic converter, Battalion Chief Jeff Holden said.

The three fires broke out around 6:30 p.m. in the area of the Lakeville Highway and East Washington Street exits. Two were minor, but one burned through a fence and scorched around 400 feet of dry grass, he said. It took about an hour to control that largest blaze.

No injuries were reported and there was no damage other than the fence.