The single-vehicle crash was reported shortly before 8 a.m. Friday near mile marker 113, according to the San Bernardino County Fire Department. Whether the driver was seriously injured was unclear.
The truck's payload of lithium ion batteries caught fire as the trailer lay overturned on the right shoulder. "This product, when involved with fire, can escalate to a thermal runaway, which requires massive amounts of water to extinguish," the Fire Department said in a statement.
Fire crews managed to get the blaze under control but the batteries continued to smolder. Investigators said there was still a chance they could reignite.
Both sides of the 15 Freeway were initially shut down at the scene. Detour routes became available late Saturday night.
"Water has been provided at this location for motorists who are stuck without water and experiencing other issues due to heat and vehicle mechanical problems," the Fire Department said. "We are actively addressing the needs of motorists stuck without water and experiencing other issues. We strongly recommend that all individuals attempting to travel northbound divert and seek alternate routes as the closure is expected to be extended due to the hazmat and suppression operations related to the truck fire."
Transportation Secretary Pete Buttigieg also spoke out about the crash Saturday, saying he was keeping an eye on it.
Shortly after 2:30 a.m. Sunday, Caltrans said fire crews had made excellent progress and were able to reopen two lanes. By 3:46 a.m., all northbound lanes were reopened.
The high temperature in Baker reached 108 degrees Fahrenheit.
The cause of the crash was under investigation.