SAN FRANCISCO (AP) — Government investigators have found that a decades-old pipe that leaked and caused a massive fire at a Chevron refinery in California was corroded, and the company knew it should have been replaced.

The U.S. Chemical Safety Board and California Division of Occupational Safety and Health issued the report Wednesday, finding the 8-inch steel pipe was installed in 1976 and ruptured due to corrosion.

The report confirmed previous findings by both the agencies and the company.

The fire created a large plume of black smoke, sending thousands of nearby residents to hospitals complaining of eye irritation and trouble breathing.

Rafael Moure-Eraso, board chairperson, said Chevron should have replaced the pipe years ago.

San Rafael-based Chevron said some of the report’s findings are consistent with its own, and the company is inspecting every pipe susceptible to the same type of corrosion.