The four people killed in a Watsonville plane crash Thursday appear to have been a family traveling to meet other family members, according to Watsonville police officials.

Two children were among those killed when the 1974 single-engine Mooney M20F crashed into a medical office building on the Watsonville Community Hospital campus around 7:30 p.m., according to Watsonville police Deputy Chief Rudy Escalante.

Emergency responders initially believed there were only two people on board, but the additional two bodies were discovered late Thursday night.

“I believe they were supposed to go meet other family members near Yosemite,” Escalante said of the family.

The plane crashed into a parking lot and skidded into the empty medical office building, Escalante said.

It crashed about 15 to 30 feet into the building, causing damage to nonstructural walls. Water damage also occurred after the crash triggered the building’s sprinkler system.

The medical office building is on the campus of the Watsonville Community Hospital, but separate from the hospital itself, hospital spokeswoman Cindy Weigelt said.

The medical building was empty at the time of the crash, and the hospital building was not affected. The crash caused a fire, but a quick response by the fire department meant that no evacuations were necessary and all areas of the hospital remained operational following the crash, Weigelt said.

The aircraft, which was registered in Santa Cruz, had departed Watsonville Municipal Airport just before it crashed, according to FAA spokesman Lynn Lunsford. The hospital campus is next to the airport.

The NTSB is investigating the cause of the crash.