The first incident involving the semi that was carrying a load of hay was reported around 3:30 a.m. at Angeles Crest Highway, according to the California Highway Patrol's traffic log.
AIR7 was over the scene as crews worked to fully extinguished the flames that destroyed the semi and left charred hay spread across lanes.
It's unclear what caused the fire. Most lanes remained closed through the morning. Around noon, the CHP said that only the far right lane and the Angeles Crest Highway off-ramp would be closed for two more hours.
Meanwhile, commuters on that stretch were met with a crash in the backup from the first incident. Westbound lanes were fully shut down at Foothill Boulevard but they were eventually reopened.
It's unclear if anybody was injured.