A vehicle burst into flames Wednesday evening in Lake Worth, sending five people to the burn unit at Parkland Memorial Hospital in Dallas, a MedStar spokeswoman said.Witnesses said the vehicle was stopped at a red light at Northwest Loop 820 and Azle Avenue about 8:15 p.m. when flames erupted, spokeswoman Macara Trusty said.The occupants, who were on fire, jumped out.Four were transported to Parkland by helicopter amublance. One was taken by ground ambulance. They ranged in age from mid-20s to mid-40s, Trusty said. Four were men, one was a woman.The Lake Worth and Fort Worth fire departments responded to put out the fire. Investigators had not determined the cause of fire, Trusty said.