The National Transportation Safety Board says a medical helicopter that crashed and seriously injured four people lost engine power shortly after takeoff near Seminole.

The helicopter crashed shortly before 1 p.m. Jan. 2 after taking off from Seminole Regional Airport en route to a hospital in Okemah where it was to pick up a patient. Authorities say the pilot, a nurse and two medics on board were injured but survived.

The NTSB preliminary report released Monday says the pilot told investigators that the aircraft's engine lost power shortly after takeoff and made a hard landing in a field near the airport about 55 miles east of Oklahoma City.