ANCHORAGE, Alaska — State transportation officials have shut down the 400-mile road to Alaska’s oil fields after “a significant flooding event,” washouts and erosion across a broad stretch between mileposts 305 and 356, according to the Department of Transportation and Public Facilities.

Repairs are underway at key damaged areas, and monitoring is taking place across a 150-mile swath of the dirt-and-gravel ribbon as melting and flooding cause concerns, the agency said a statement Monday.

The “emergency closure” began Saturday after a “major washout” ripped through the road at milepost 315, the agency said.

A “failed culvert” at the site caused an 80-foot-wide, 30-foot-deep breach across the entire road, the agency said.

The milepost is about 100 miles from Deadhorse, the industrial hub for the giant Prudhoe Bay oil fields.

The closure is in place between mileposts 305 and 356. But state transportation officials are also eyeing potential issues far to the north and south. The events include ice jams flushing near the major washout site, the state said on social media.

The Dalton, also known as the Haul Road, provides the only road access to the state’s economically vital oil patch on the North Slope.

The dirt-and-graven ribbon starts about 85 miles north of Fairbanks and travels to Deadhorse. The industrial town also serves as a jumping-off point for tours to the Arctic Ocean. The road was a star feature of the former reality TV show “Ice Road Truckers.”

The National Weather Service has issued flood warnings and watches on the North Slope due to rapidly melting snow, including along the Sagavanirktok River that parallels the Haul Road in much of the region.

Shannon McCarthy, a spokesperson with the Alaska transportation agency, said trucking companies are aware of the washout.

“We’re providing information to the trucking industry so many have not gotten onto the highway,” she said in a statement.

“Since the onset of the event, (Alaska state transportation) crews and contractors have been working to stabilize the site, mobilize materials and equipment, and prepare for urgent repairs,” the agency said in a statement Monday.

“Additional areas of concern have emerged along the corridor, including water overtopping at MP 318, shoulder damage between MP 321 and 325, and impounded water at MP 351 due to a partially blocked culvert,” the statement said. “A new erosion site at MP 402 is also being monitored following rip rap placement to prevent further degradation.”

Near the main washout at milepost 315, crews are using excavators, multiple haul trucks and other heavy equipment to reach the base of the cut. They plan to install “two 48-inch steel culverts with a 36-inch overflow pipe,” the statement said.

Erosion at milepost 402 is near the erosion that occurred last year not far from the North Slope oil patch.

That area is “historically vulnerable” to erosion and crews are working there to strengthen sections that could damage the road, the statement said.

Springtime melting and flooding in that northern end of the Haul Road also led to closures and caused significant damage about a decade ago.

“The agency currently estimates the road will remain closed through Wednesday, though it will continue to monitor the situation and provide daily updates at 9 a.m. and 7 p.m. daily until the highway is reopened,” DOT’s statement said.

“Our primary goal is to safely restore one-lane access as soon as conditions allow, with traffic control measures in place throughout the ongoing repair work,” the statement said.

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