RICHMOND — Authorities were searching the Kennebec River Friday morning for a Richmond man who was reported missing Thursday night and whose boat was found, running and unoccupied, aground on Swan Island.

Mark Johnston, 64, was reported overdue at 9:20 p.m. Thursday after he had gone out onto the river with plans to take his boat from a mooring on the river to the Richmond town docks, so it could be hauled out of the river on Friday.

A search got underway Thursday night and his 32-foot recreational motor boat was found aground, downriver from Richmond on the west side of Swan Island, with its engine running and navigational lights on. No one was on board, according to Jeff Nichols, spokesman for the Maine Marine Patrol.

Searchers including firefighters from Dresden, Woolwich, and Bowdoinham as well as the Marine Patrol, Richmond Police, the Richmond Harbormaster, a 29-foot US Coast Guard Vessel, and a Coast Guard helicopter out of Cape Cod searched the river by air, land and water overnight until about 2 a.m. when the search was suspended. It resumed this morning.

A Marine Patrol airplane circled over the river Friday morning as part of search efforts, as well.

Nichols said State Police and Marine Patrol divers were on the scene Friday morning, using a side scan sonar device to look underwater, near the town docks in Richmond.

He said Johnston had indicated his plans were to move his vessel from its mooring to the Richmond docks around 4:30 p.m. Thursday so it could be hauled out Friday.

His vehicle was discovered parked near the town boat launch Thursday after he was reported overdue.

This story will be updated.

Keith Edwards — 621-5647

kedwards@centralmaine.com