PORTLAND – Investigators Monday were seeking the cause of a weekend plane crash off the Maine coast that claimed the lives of a New Jersey couple.

The bodies of Edward and Maryann Mainardi were recovered Sunday afternoon, less than three hours after the Coast Guard launched a search for their Cessna 337 Skymaster as it was en route from Millinocket to Caldwell, N.J.

Air traffic controllers from Brunswick Naval Air Station had lost communications and radar contact with the aircraft, which crashed about a half-hour after takeoff.

Edward Mainardi, a semiretired lawyer, was a pilot and the couple had a vacation home in the Millinocket area, according to Jeff Campbell, supervisor of Millinocket Municipal Airport.

The National Transportation Safety Board is investigating the crash.

Investigators were focusing their attention on three areas: the pilot, his experience and medical history; the condition of the plane and its maintenance records; and air traffic controller radar data, weather conditions and radio traffic, said Luke Schiada, senior air safety investigator for the NTSB’s Eastern region.

Schiada said his agency planned to coordinate with the plane’s insurer on whether it intends to try to recover the aircraft. In the event that portions of the plane are recovered, an NTSB investigator may travel to Maine, he said.

Flying conditions out of Millinocket were fine at the time of the crash, Campbell said, noting that the plane could fly at an altitude above the rainy weather that was moving in.

“I’ve been wrestling with it all day, what could have caused [the accident],” Campbell said.

The Coast Guard’s air and sea search quickly zeroed in on an area 18 miles east of Portland where a fuel sheen and debris field were found.

The Mainardis owned the Cessna for 28 years and were looking to sell it, Campbell said. Edward Mainardi also had a larger plane and employed two pilots to fly it.

The couple had planned to return to Maine on the Fourth of July, Campbell said.

“They told me today that they’d be back in two weeks,” he said Sunday.