The Oxford County Sheriff’s Office says it does not know why someone has been stealing cars and pushing them into the Saco River.

Sgt. Tim Ontengco told WCSH-TV on Sunday that the thefts are “crimes of opportunity” because the victims had left their car keys in the vehicles. Ontengco could not be reached Sunday night.

Four cars were reported stolen in Brownfield and Hiram on Thursday and Friday. Ontengco said a concerned citizen spotted two stolen vehicles floating in the Saco River and notified authorities on Sunday. Those cars were towed from the river, near the Hiram and Brownfield town line on Route 113.

The remaining cars have been found. One stolen vehicle was torched and the fourth car was damaged by the person who stole it. No one has been arrested.