The truck, a contract vehicle carrying eight containers of letters and headed to the Ontario Airport, rear-ended another big rig and caught fire around 1:30 a.m. Tuesday on the northbound 57 Freeway between East Birch Street and Lambert Road, California Highway Patrol and U.S. Postal Service officials said.
No injuries were reported, highway officials said.
U.S. Postal Service officials said to call your local post office if your mail doesn't reach its destination within a few days.
The U.S. Postal Inspection Service is investigating the accident.