ROWLETT, Texas (AP) — Investigators found main rotor impact marks next to a tail boom that separated from a helicopter just before a crash near Dallas, the National Transportation Safety Board reported Thursday.

In a preliminary report, the NTSB said impact marks were consistent with in-flight contact, and investigators found no evidence of any pre-separation failures on the aircraft.

A student helicopter pilot and a flight instructor died in the March 25 crash in a vacant lot in a Rowlett, Texas, commercial strip.

Witnesses reported seeing the helicopter lose its tail rotor and spin uncontrollably before crashing and burning.