HOST: Inspectors from the U.S. Chemical Safety Board are in Richmond to brief the City Council on Tuesday evening and residents on their probe into the Chevron refinery fire. KQED's Aarti Shahani reports the federal agency has more questions than answers.

AARTI SHAHANI: Don Holmstrom, the Western Regional Director for the Chemical Safety Board, wonders if Chevron management made the wrong decision when they decided to keep an oil processing unit running after a leak was already discovered. He asks why workers were even in the vicinity when the fire occured. His agency has interviewed 80 people so far.

DON HOLMSTROM: "We're going to do testing of samples of crude, samples of the gas oil that was in the line. We're also going to be looking at the piping that failed, from a metallurgical perspective, in terms of various thickness measurements."

SHAHANI: Holmstrom called the corroded pipe "thin," but would not say how thin it was. He expects their investigation into the root cause of the fire will not be complete for many months.

I'm Aarti Shahani, KQED News.