SAN CLEMENTE – A man was killed in a fiery crash when a flatbed lumber truck rear-ended a pickup that was towing a 1950 Oldsmobile in the southbound lanes of I-5 Thursday afternoon, causing traffic to back up for miles, officials said.

Firefighters and California Highway Patrol officers were called to the crash about 1 p.m. after receiving reports of someone trapped in a pickup near the El Camino Real off-ramp, said Capt. Steve Concialdi of the Orange County Fire Authority.

The driver of the pickup died at the scene, and the body was freed by firefighters from the crushed pickup shortly after 5 p.m., Concialdi said. The man, who has not been identified, was driving a 1984 pickup with Washington plates and was towing a 1950 Oldsmobile on a dolly.

The driver of the lumber truck, a 55-year-old man, suffered minor back injuries and declined to be taken to a hospital.

The pickup was engulfed in flames and the Oldsmobile and the lumber truck sustained significant damage. The fire was under control in 15 minutes, Concialdi said.

Investigators are trying to determine in which lane the vehicles were traveling and whether speed played a factor in the crash, CHP Officer Aaron Rothberg said.

All lanes of southbound I-5 were shut down for several hours, forcing commuters to use the right shoulder to pass the crash scene. The slow lane reopened at 4:15 p.m,. and all other lanes were open around 7.

CHP is asking anyone who witnessed the crash to call 949-487-4000.

Staff writer Scott Schwebke contributed to this report.

Contact the writer: 714-704-3788 or shernandez@ocregister.com