There is no evidence that structural failures caused a March airplane crash in north Mississippi that left one man dead and his son injured, according to a report published Wednesday by the National Transportation Safety Board.

Authorities were alerted to the March 31 crash after a small private plane had not returned to the airport from which it had taken off. A cellphone belonging to one of the plane’s occupants was pinging off a rural road near the college town of Oxford.

The report revealed that two friends of the father, who was the pilot, observed the airplane flying around 7 p.m. After the pilot still hadn’t responded to calls and texts the next day, local authorities were notified. When deputies arrived at the area, they found the plane’s wreckage and the pilot dead. His son, initially reported as missing, was later found around midnight and taken to an area hospital with injuries.

One friend noted that it was unusual for the pilot to fly in the evening.

The left wing and landing gear of the plane were suspended in a tree about 15 feet (4.5 meters) from the main wreckage. Tree heights near the accident site were estimated at 75 feet (23 meters) tall.

The agency’s findings are preliminary and could change in the future.