SAN FRANCISCO (CBS SF/AP) – U.S. chemical safety investigators are calling on California to strengthen its oversight of refineries and chemical facilities after investigating the cause of an intense fire at Chevron Corp.’s Richmond refinery.

The U.S. Chemical Safety Board on Monday released an interim investigative report of the Aug. 6 refinery fire, which was caused by a corroded pipe that failed and released massive vapor cloud.

The report says Chevron and the entire industry knew that the use of crude oils with higher sulfur content would cause higher rates of corrosion in their old pipes, but did not do enough to replace aged equipment.

The investigators say the state and federal governments should create new regulations that require companies to use the “safest feasible technologies and materials.”

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