A former U.S. Postal Service carrier has been sentenced to 18 months in federal prison for selling marijuana on his mail route.

Prosecutors said 48-year-old Ronald Berkan of Vernonia pleaded guilty in April to distribution of marijuana to a person under 21.

Investigators said they arrested Berkan after Lake Oswego police arrested a 19-year-old who claimed he had been buying marijuana from Berkan since high school.

As part of a plea agreement, Berkan resigned from the Postal Service in April after 15 years of service.

U.S. Attorney Karin Immergut, the chief federal prosecutor for Oregon, said Berkan violated the public trust in addition to selling marijuana to a teenager.