Air traffic controllers lost radar and radio contact with a Cessna 172 that departed Kahului Airport for Molokai on Saturday night, said Federal Aviation Administration spokesman Ian Gregor.
The plane was five miles north-northeast of Kahului at 7 p.m., Gregor said.
"The Coast Guard is searching for the plane," he said in email at 8:46 p.m.
At 9:47 p.m., emergency dispatch operators said debris was spotted six miles off Maui. But that report was not confirmed.
Shortly afterward, Fire Services Chief Lee Mainaga said he heard the transmission about debris, but it remained unconfirmed because U.S. Coast Guard officials could not be contacted.
Maui dispatch operators received an alarm that a Cessna aircraft possibly crash landed about three miles northeast of Kahului Airport, most likely in the ocean, Mainaga said.
Dispatch was notified by the Honolulu Airport tower, which reported the aircraft was flying from Maui to Molokai.
The Coast Guard's Joint Rescue Coordination Center in Honolulu launched rescue crews aboard a MH-65 Dolphin helicopter and an HC-130 Hercules airplane from Barbers Point on Oahu, officials said. The crew of the Coast Guard Cutter Ahi, homeported in Honolulu, was deployed to the area to assist.
Maui firefighters and police began conducting land searches on Maui's north shore.
Mainaga said Paia firefighters searched the coastline from Kuau to Pauwela, but crews found nothing as of 9:05 p.m.
The Cessna 172S is a four-seat, single-engine, fixed-wing aircraft. Coast Guard officials said it was unknown if anyone other than the pilot was aboard.