Updated

Two adults and two children were killed when a small plane crashed into a medical building, federal investigators said Friday.

Authorities initially reported that two people died in the Thursday night crash on the grounds of the Watsonville Community Hospital. The plane went into an unoccupied office building, and no one on the ground was hurt.

Four bodies were found after authorities extracted the 1974 single-engine Mooney M20 from the building overnight, said Michael Huhn, the National Transportation Safety Board's lead investigator at the scene.

The names of the victims have not yet been released.

The pilot had just taken off from nearby Watsonville Municipal Airport when the plane went down around 7:30 p.m., Federal Aviation Administration spokesman Lynn Lunsford said.

Thomas Arnold was in the parking lot next to the hospital's administration building when he heard the plane overhead. He told the Santa Cruz Sentinel that the plane came careening sideways across the parking lot about 15 feet above his head.

"I saw two faces and two big sets of eyes," said the 34-year-old Arnold, whose fiancee was in labor inside the hospital.

Another witness, George Benson, told the Sentinel that he watched the plane take off and saw the pilot appear to attempt to clear a line of fog. "He was heading toward the coast and tried to climb," Benson said. "From the time he took off he was going too steep, too slow."

The plane went down into a parking lot in front of the medical office building and skidded about 50 yards to 75 yards before crashing into the building, Deputy Police Chief Rudy Escalante said.

Photos showed the charred tail end of the aircraft sticking out from the one-story building, part of which had been blackened by smoke. Damage appeared contained to an area at the end of the building.

Escalante said the building appeared to be structurally sound despite the crash.

Watsonville is located near Monterey Bay, about 90 miles south of San Francisco.