Authorities launched a search Tuesday for a medical helicopter that vanished while carrying a patient and medical crew.

The LifeGuard Alaska helicopter, which was heading from Cordova to an Anchorage hospital, disappeared Monday sometime after 5:18 p.m., authorities said. The helicopter crew had made a satellite phone call around that time, but it was not a distress call, said Coast Guard Lt. John McWhite.

A patient, pilot, doctor and nurse were aboard the helicopter, said Providence Alaska Medical Center spokeswoman Becky Hultberg. Their names were not released.

The helicopter's last known position was Esther Island in Prince William Sound, about 75 miles southeast of Anchorage, said Lt. j.g. Johna Rossetti. The trip from Cordova to Anchorage is about 150 miles by air.

A Coast Guard cutter left Cordova just before 5:30 a.m. Tuesday and was making its way through Prince William Sound, Rossetti said. Bad weather had hampered search efforts overnight.

The patient's condition and the reason for the flight were not immediately known.

LifeGuard Alaska is an air ambulance service operated by Providence Alaska Medical Center in Anchorage.