The aftermath of the plane crash that killed NASCAR legend Greg Biffle and his family is now being detailed in dramatic, newly-released 911 audio. Multiple calls were obtained by TMZ on Tuesday, January 6, painting a picture of the immediate aftermath of the crash that killed Biffle, 55, his wife, Cristina, his 14-year-old daughter, Emma, and his 5-year-old son, Ryder, on December 18. One caller on site at North Carolina's Statesville Regional Airport described "a huge fire" after a "small, mid-sized jet" crashed. "I don't know how many people were on board, but I do know there's at least two pilots," the caller said. "Probably at least four passengers." Greg Biffle's Holiday Card Arrived at Friends' Homes After Fatal Plane Crash In addition to the Biffle family, the crash killed pilot Dennis Dutton, his son, Jack, and NASCAR motorhome driver Craig Wadsworth. Another caller, who was playing golf at Lakewood Golf Course near the airport, told a 911 dispatcher, "We just have a plane fly over our heads and crash into the tree line." The individual said the plane went "straight downward," resulting in a "huge explosion." The dispatcher on the call warned the golfer not to go near the crash site. A third caller said the fire from the crash "spread from the golf course until the end of the runway." The plane, which belonged to Biffle, crashed just minutes after taking off from and attempting to return to Statesville Regional Airport. It is not known who was piloting the plane at the time of the incident. The crash remains under investigation, according to the National Transportation Safety Board. "Our representative with the National Transportation Safety Board disaster assistance division is continuing to work with the family members and loved ones of those who lost their lives in this accident," NTSB board member Michael Graham said in a December 20 press conference. "And I want to thank the family members who have been assisting our team during this terrible time." Graham added, "We do not know the circumstances that led the aircraft ... to return to the airport but that is the focus of our investigation. Early indications from multiple sources indicate that the airplane was stable on approach, configured for landing with the landing lights on, but the aircraft was coming in low." Dan Rose, a former military pilot and aviation attorney, exclusively told Us Weekly that it could take "close to two years" until the NTSB releases the final results of their investigation. NASCAR Icon Greg Biffle Had Poignant Final Social Media Post Before His Death The extended families of those killed in the crash released a statement on the evening of the tragedy. "We are devastated by the loss of our loved ones," the statement read. "This tragedy has left all of our families heartbroken beyond words," the families said. "Greg and Cristina were devoted parents and active philanthropists whose lives centered around their young son Ryder and Greg's daughter Emma (mother - Nicole Lunders)." The statement described 14-year-old Emma as "a wonderful human being with a kind soul who was loved by many people" and 5-year-old Ryder as "an active, curious and infinitely joyful child." A memorial service for the Biffles and the other crash victims is scheduled for January 16 in Charlotte.