A petroleum supplier and his wife apparently were killed by carbon monoxide fumes in their enclosed horse-riding arena in Harrisville, according to police and the assistant state medical examiner.

Authorities said the deaths of Robert Ruben Field, 51, and Kathleen Field, 50, appeared to be accidental. Police Chief Rich Dean said there was no evidence of foul play.The couple's bodies were found about 8 a.m. Monday by their son, Bret R. Field of Ogden.

Field owned Field Oil Inc., in Ogden, and co-owned two Klassy convenience stores.

Roy Police Sgt. Edward Rhoades, who also is an assistant medical examiner, said the two appeared to have been dead no more than 12 hours.

He said they apparently entered the unheated arena to work on stored equipment and were overcome by fumes from a running motor home engine. They may have run the engine to warm the motor home, he said.

Dean said the well-sealed arena is about 30 feet by 50 feet and about 25 feet tall. He said it appeared that all four motor homes stored in the building had been run recently.