U.S. Coast Guard flight logs indicate a mechanical problem prevented a rescue helicopter from responding to the scene of a fatal January air ambulance crash in Alaska.

CoastAlaska reported Tuesday that the logs indicate the helicopter that should have flown within 30 minutes of the call from Sitka to the crash site about 22 miles (35 kilometers) west of Kake was grounded until the next morning due to an engine malfunction.

The station reports there was subsequently no aerial search conducted for the first 12 hours after the Beechcraft King Air 200 vanished from radar.

Officials say a Coast Guard cutter and local search and rescue teams responded overnight.

Authorities say it is still unclear what caused the crash in which a pilot, paramedic and nurse were lost at sea.