A 15-year veteran Coast Guardsman who surfaced Sunday after disappearing four months ago and touching off an extensive air, land and water search is the subject of an investigation into drug use, a Coast Guard spokes­man said today.

At the time of his disappearance, Petty Officer 1st Class Russell Matthews was being investigated for illegal use of drugs, specifically marijuana, said Coast Guard spokes­man Chief Warrant Officer Gene Maestas. Illegal drug use is an offense that could result in a Coast Guard member’s discharge.

Matthews turned up at about 7:30 p.m. Sunday, police said in a CrimeStoppers bulletin issued Tuesday.

The father of two showed up at his wife’s North Shore home but did not live there, Maestas said.