Four young men have been killed in a small plane crash at a southern Utah airport, authorities report.

The downed single-engine Cessna 172 was found at about 6am on Saturday in southern Utah about four hours after crashing some 400 feet from the runway, said Marc Mortensen, assistant to the St. George city manager.

The crash occurred as the pilot was attempting to take off, he said.

Fatal: A small plane crashed at a Utah airport killing all four people on board

The victims were identified as 28-year-old Colby Hafen and 20-year-old Christopher Jordan Chapman, both of Santa Clara; 23-year-old Tanner Holt, of Washington City; and 22-year-old Alexander Metzger, of St. George.

Officials believe all four passengers aboard the single-engine Cessna 172 were killed on impact.

A security video from the small, dusty airport captured the airplane lifting off the runway, moments before the crash. However, the small aircraft is out of sight when it crashes.

According to family speaking to the Deseret News, Holt was a trained pilot who had flown commercially, though they were not able to confirm if he was the one flying the plane when it went down.

The plane crashed under 'unknown circumstances,' Federal Aviation Administration spokesman Ian Gregor said.

Investigation: Authorities are working to determine the cause of the crash which killed Colby Hafen, 28, pictured

Memory: His family say they'll remember the uncle and brother for his contagious smile and ability to light up a room

In a statement released by the family of Mr Hafen, they described him as a 'wonderful' son, brother and uncle.

'He could always bring a smile to anyone's sad day and had the most loving and giving heart,' they wrote. 'He could light up the room with his contagious smile and infectious personality.'

He worked with his father in insurance according to his family and served as a Mormon missionary to Oregon.

Mr Chapman's 13-year-old sister Brecken described her brother as a caring young man who always put others ahead of himself.

Unexpected: Alex Metzger, 22, was another victim of the wreck discovered approximately four hours after its mysterious crash some 400ft from an airport runway

Pilot: Tanner Holt, 23, was a trained pilot who according to family had flown commercially but has not been confirmed as the one operating the plane when it went down

She told the Salt Lake Tribune he planned to attend the University of Utah this coming fall in hopes of becoming a doctor one day.

'He was really funny,' she said. 'He had a memorable smile. He was a good brother and a hard worker.'

His flight Saturday morning she estimated may have been only his second time ever riding on an airplane. She said she last saw her brother the night before the crash and didn't know of his plans to fly.

The area saw windy conditions on Friday and later Saturday.

But there was no severe weather at the airport during the early morning hours on Saturday, National Weather Service meteorologist Monica Traphagan told The Spectrum of St. George.

Big brother: Described as a funny and good big brother, Jordan Chapman, 20, planned to attend the University of Utah this coming fall to become a doctor his 13-year-old sister said

The airport has been in operation at its current site for about one and a half years.

It does not have a radio tower and pilots use an automated system to communicate with one another when landing or taking off.

The wreckage was found by an airport crew making a routine safety check of the property.
Federal authorities were investigating the cause.

It normally takes the National Transportation Safety Board months to discover the cause of a crash.