(CNN) — Los Angeles drivers have been warned of significant travel headaches after a major fire over the weekend forced the indefinite closure of a downtown portion of Interstate 10, one of the city’s major traffic arteries.

Los Angeles Mayor Karen Bass described the closure as a “crisis” for a city already notorious for its traffic woes. She urged travelers to brace for delays and plan alternative routes as the interstate remains shut down in both directions in downtown Los Angeles near Alameda Street.

Ahead of the Monday morning commute, a citywide alert was sent to residents’ cell phones warning that the freeway “will be closed indefinitely” and to “expect significant traffic.”

More than 300,000 vehicles travel through the freeway corridor every day, California Gov. Gavin Newsom said.

“It’s of significant consequence to the economy, to the health and safety of Angelenos,” Newsom said. “The impact to our schools, to vulnerable communities – all of that we take very seriously, and we’re sober and mindful of the urgency to get this open.”

The city is scrambling to assess the safety of the roadway and repair the damage caused by a raging fire at a storage yard early Saturday that spread under the freeway to ignite a second storage facility, ultimately consuming about 80,000 square feet and destroying several vehicles, according to the Los Angeles Fire Department.

There is no estimated timeline for reopening the stretch of the busy interstate, and Bass warned Sunday that the issue “is not going to be resolved in one or two days.”

Those impacted by the shutdown are advised to work from home if possible, the state Department of Transportation said. Nearby school bus routes are also likely to change, though public schools will remain open, the LA Unified School District announced.

Newsom declared a state of emergency for Los Angeles County due to the closure.

“The state is mobilizing resources and taking steps to ensure any necessary repairs are completed as soon as possible to minimize the impact on those traveling in and around Los Angeles,” the governor said in a statement.

The cause of the blaze is being investigated by the state fire marshal. The investigation is expected to conclude Monday morning, Newsom said at a Sunday news conference.

Once a hazardous materials investigation is complete, structural engineers will be able to go in to determine the extent of the damage, city and state officials said.

Hazmat teams will work around the clock to clean up the damage on Interstate 10, according to Newsom, who said the scale of the fire’s damage is “substantially greater” than the collapse of a portion of Interstate 95 in Philadelphia in June.

“You name it, we saw it stored at this site,” said Newsom, who toured the location on Sunday. Wooden pallets, cars filled with gas and boxes of oranges have all been found under the Los Angeles bridge, officials said.

Firefighters responded to reports of a fire around 12:30 a.m. Saturday at a 200-by-200-foot storage yard “with pallets, trailers and vehicles well involved in fire” and buildings that were exposed, according to the fire department.

“Wind pushed the heat and the flames under the freeway, and across the street ignited a secondary storage yard,” Fire Chief Kristin Crowley said Sunday.

The bulk of the fire had been extinguished within three hours and firefighters were able to save three nearby commercial buildings, Crowley said. More than 160 firefighters responded to the incident, she added.

No injuries have been reported due to the blaze, the fire chief said.

When asked by reporters why the flammable material was allowed to be stored under the bridge, the governor said, “That’s all being assessed.”

Newsom said the tenant of the site is in violation of their lease. “We’re in litigation, their lease has expired and we have been aggressive in addressing concerns as it relates to the lease itself,” he said.

Officials believe the tenant “subleased the space … with multiple subleases, that’s part of the litigation posture,” Newsom said.

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