Multiple brush fires caused by trips in an electrical transmission line Wednesday afternoon briefly blocked one lane of the New York State Thruway southbound near the Rockland/Orange County border, officials said.

A dump truck driver working with E. DeMarino & Sons of Tuxedo was working at a construction site in the town and had the dump bed up when he backed into a high-voltage transmission cable, Orange & Rockland Utilities spokesman Mike Donovan said.

The cable, which runs from Harriman to Sloatsburg, was knocked to the ground and was still live, Donovan said.

"The insulator on the cable broke," he said. "What happens is the system continually tries to reset itself, and in trying to reset itself, it energized the wires, and the wires heated up," causing a series of trips down the line and igniting "at least two" brush fires.

An adjoining transmission line, running from Sloatsburg to South Mahwah, N.J., was knocked out briefly by the cascading trips line but reset itself by 2:15 p.m. and did not ignite any fires, Donovan said. The Harriman-Sloatsburg line was not expected to be repaired until midnight Wednesday, he said.

Utility officials are investigating whether stockpiling of compost materials at the site by the contractor may have changed the grade of the ground there, leaving less than the 15 feet of clearance required for overhead lines, Donovan said.

A man answering the phone at E. DeMarino & Sons Wednesday afternoon said, "No comment" and hung up on a reporter without identifying himself.

The 69-kilovolt cables are bulk transmission lines, so there was no effect on electrical service in the area, according to Donovan.

No injuries were reported as a result of the downed cable.

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Smoke from one fire, at Thruway mile marker 34.9, about three miles north of Exit 15A/Sloatsburg-Suffern, forced authorities to shut down the right southbound lane at 2:04 p.m., the Thruway Authority said. The lane was reopened 18 minutes later.

Multiple fire units from Rockland and Orange counties were battling the brush blazes, officials said. State Police said no traffic accidents had been reported, and a Metro-North spokesman said service was normal on the Port Jervis and Pascack Valley lines.