Nine people were killed when a private business jet crashed into a mobile home park in Palm Beach County, southern Florida, on Sunday evening, US Transport Secretary Sean Duffy said. Whether anyone on the ground was also injured remained unclear.

The Learjet 60, valued at about $2 million, was travelling from an international airport in Austin, Texas, to the Bahamas with nine people aboard. It made a sharp right turn before plunging from roughly 8,000ft, or 2,440 metres, and crashing.

At least one mobile home was struck. A huge fireball was documented at the site, where the impact left a large crater amid burning aircraft wreckage and the remains of the damaged home. Photographs show flames spreading through scattered debris beside a road, with thick dark smoke rising above nearby buildings and palm trees.

Preliminary assessments suggested that the aircraft hit a tree and brought down power lines. Those details do not establish why the jet descended, and the cause of the crash remains unresolved. One witness described a sound resembling a missile.

Duffy described the crash as a terrible tragedy and said the Federal Aviation Administration was sending a team to the scene to assist the investigation.

Palm Beach fire services designated the crash a mass-casualty incident. Several roads around the site were closed until further notice, and the sheriff’s office urged motorists to avoid the area. Alongside establishing the cause, a central unresolved question was whether the toll extended beyond those aboard the aircraft.