Railroad officials and central Oregon sheriff's detectives are trying to determine who pushed large boulders onto railroad tracks near a Madras, Ore., trestle twice in recent weeks.

A freight train locomotive hit the first boulder and suffered damage. Burlington Northern Santa Fe spokesman Gus Melonas says train conductors spotted the second boulder last week and stopped the train in time.

No one has been injured. But Jefferson County sheriff's Detective Starla Green says authorities think someone pushed 200- to 300-pound boulders onto the tracks in an effort to derail a train into a canyon.

They're looking for a red dune buggy seen in the area around the time of the incidents.

The first such incident occurred in May.

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