Four Utah men died in the crash of a single-engine, private plane early Saturday.
The Cessna 172 crashed under unknown circumstances at the St. George Municipal Airport, said Ian Gregor, communications manager for the Federal Aviation Administration's Western-Pacific Region. "We are not certain what phase of flight the aircraft was in when it crashed," he said.
The single-engine plane crashed in the early hours but was not discovered until 6 a.m. when airport workers arrived to do routine safety checks of the grounds.
The plane crashed about 300 feet from the south end of the runway.
Marc Mortensen, assistant to the St. George city manager, told KUTV Channel 2 that the four men killed were from the area.
Mortensen said it appears everyone on board died on impact. The victims' next of kin were being notified, he said.
Gregor said the FAA and National Transportation Safety Board will investigate the crash.
A basic preliminary report is posted on NTSB's website within a week or two of an accident, he said.
Gregor added that it typically takes the NTSB months to determine an accident's probable cause.
Because of the location of the crash, operations at the St. George airport on Saturday were not being affected.
The airport does not have a radio tower. It works with an automated system in which pilots can communicate with one another during landing or takeoff.