LOS ANGELES — Lax oversight by California's transportation agency contributed to a destructive blaze last year that consumed a vital section of a Los Angeles freeway used by hundreds of thousands of commuters, according to a state audit.

While authorities determined the fire was arson, the Office of the Inspector General for the California Department of Transportation said the agency conducted its required annual inspections of lots under Interstate 10 only five times in 15 years and failed to fully document those inspections. When Caltrans discovered problems, it failed to act.

“Caltrans could have—and should have—done more to make this property safer for the motoring public who traveled above it,” according to the report released last Thursday.

Caltrans said in a statement that since the fire, it has implemented new safety measures and also paused new leases for lots to better protect the state’s highway system.

“Safety is Caltrans’ top priority, and the department takes the results of this audit report seriously,” the agency said in its statement.

Flammable materials were being illegally stored on the land under the freeway, which Caltrans was leasing to the private company Apex Development Inc, the report said. The blaze burned through about 100 columns, spreading over what authorities described as the equivalent of six football fields and forcing the closure of a mile-long stretch of I-10 near downtown LA.

Officials had estimated the initial repairs, which were expected to be covered by federal funds, would cost $3 million.

During the few inspections Caltrans conducted of the property, it discovered several hazards including multiple piles of wooden pallets stacked high and flammable materials like solvents, oils fuels, and more. Apex was also illegally subleasing to six other companies, the agency alleges in a lawsuit filed before the fire.

There were also “previous warning signs” that Caltrans did not react to, including a 2017 massive freeway fire in Atlanta under Interstate 85, according to the audit. In this incident, construction materials stored under the overpass were set on fire and collapsed a 92-foot section of the freeway.

In 2022, another fire broke out in a space under the Los Angeles freeway right next to the area that caught on fire last fall, which “did not seem to trigger a notable response from Caltrans nor did it elicit any sign of urgency to prevent another fire from happening,” the report said. It took the agency four months to complete an inspection after that incident.

According to the report on the 2023 blaze, Caltrans said it is “somewhat limited to act on its own when necessary due to various landlord-tenant laws and its own limited expertise."

The audit recommended Caltrans ensure regular inspections, train staff on identifying lease violations and streamline the approval process for determining when to take legal action.

Caltrans has 60 days to create a corrective action plan and is asked to provide an update every six months until all issues have been addressed.