Two people were reported dead after a fiery plane crash near Discovery Bay Tuesday afternoon, according to Contra Costa County officials.

Around 2 p.m., county fire crews responded to reports of a plane crashing near Marsh Creek Rd in Byron, four miles from Byron Airport.

Crews arrived to find the plane, a homebuilt single-engine Glasair III , fully engulfed in flames, according to Contra Costa County Sheriff’s spokesperson Jimmy Lee.

Lee said that one fatality was confirmed by responding crews. Hours later, at around 7 p.m., Lee announced that another body was found in the wreckage. Details about the victims were not immediately available.

The cause of the crash was still unknown Wednesday afternoon, according to Ian Gregor, public affairs manager for the Federal Aviation Adminstration's Pacific Division.

Gregor said that the FAA and National Transportation Safety Board (NTSB) would investigate the crash. The NTSB was tapped to lead the investigation

"The NTSB investigator usually posts a basic preliminary report on the agency’s website, www.ntsb.gov, within a week or two of an accident. However, it typically takes NTSB months to come up with a probable cause for accidents," said Gregor in a statement to KTVU.

The plane is registered to DSB Inc., located in Fernley, Nev., according to the FAA website.

Pilots from the area have said they believe the plane came from a nearby private airstrip called Funny Farm Airport, according to Keith Freitas, director of airports for Contra Costa County.

The airstrip, located near Penny Lane just outside of Brentwood, has been around for several decades, Freitas said.

The owner of the airstrip appears to be the same person to whom the plane is registered, based on FAA records. 

Joshua McLean, 19, said he witnessed the plane fall from the sky after hearing the engine whirring overhead.

"It was about 1,500 feet off the ground and corkscrewing toward the ground," McLean said.

"It seemed as though he had just lost control of the plane," said McLean, whose family operates a farm next to the crash site. "I didn't see the impact because it was below the tree line."

"When it hit the ground, you could feel the rumble," he said.

The plane came to rest in a neighbor's property. McLean said he drove to the crash site and called 911.

"From the nose to the tail, the plane was almost completely gone," he said of the wreckage. "There was just the tail and smoke and fire coming from it."

He said he saw a body at the crash site.

Emergency responders arrived about five minutes after McLean got to the scene as local farmers gathered to watch, he said.

The company that manufactured the plane assembly kit, Glasair Aviation, advertises on their website that their Sportsman-line of amateur construction kits are "The Only Airplane You Can Build In Two Weeks."

According to its website, Glasair Aviation is a subsidary of Stoddard-Hamilton Aircraft, was started in 1980 and lists itself as "one of the largest, most well-established kitplane manufacturers in the world." 

Byron Airport is located in a rural section of far eastern Contra Costa County about 20 miles northeast of Livermore.