LITITZ, Pa. — Three of the five people injured in a single-engine plane crash in central Pennsylvania over the weekend were sent from a Lancaster hospital to a burn center for treatment, authorities said Monday.

Two patients were flown to the Lehigh Valley Health Network’s burn center and a third was driven there by ambulance, according to a spokesman for Lancaster General Hospital, where all five occupants were taken immediately after the crash. The other two patients were released Sunday night from Lancaster General, he said in an email.

The plane burst into flames as it crashed shortly after takeoff Sunday from Lancaster Airport and was destroyed. It landed in a parking lot of the Brethren Village retirement community in Lititz, some 75 miles (121 kilometers) west of Philadelphia.

Lehigh Valley Health Network spokeswoman Jamie Stover said she was not permitted to confirm that her facility treated anyone without first being told the patients’ names, which authorities have not released.

The Beechcraft Bonanza plane, registered to Jam Zoom Yayos LLC in Manheim, not far from the airport, went down just after 3 p.m. No one was killed in the fiery crash and no one was injured on the ground, the Federal Aviation Administration said. FlightAware said the plane was headed to Springfield, Ohio.

The National Transportation Safety Board said it has opened an investigation and is working with the FAA, which it said has someone at the site to examine it and gather documentation. Investigators will look into the pilot, the aircraft and the operating environment, the NTSB said. That will include gathering recordings of air traffic control communications, flight tracking data, witness statements, surveillance video and aircraft maintenance records.

A preliminary report is expected within 30 days of the accident, while an investigation can take 12 to 24 months to complete, it said.

A message seeking comment was left Monday for the airport’s operations director.

Witness Brian Pipkin was driving when he noticed the plane veer to its left.

“And then it went down nose first,” Pipkin said Sunday. “There was an immediate fireball.” He called 911.

Air traffic control audio captured the pilot reporting that the aircraft “has an open door, we need to return for a landing.” An air traffic controller is heard clearing the plane to land, before saying, “Pull up!” Moments later, someone can be heard saying the aircraft was “down just behind the terminal in the parking lot street area.”