BLACK ROCK DESERT, Nevada (AP) — Muddy roads flooded by a summer storm that left tens of thousands of partygoers stranded for days at the Burning Man counterculture festival had dried up enough by Monday afternoon to allow them to begin their exodus from the northern Nevada desert.

Event organisers said they started to let traffic flow out of the main road around 2 pm local time — even as they continued urging attendees to delay their exit to help ease traffic on Monday. About two hours after the mass departure began, organisers estimated a wait time of about five hours.

Organisers also asked attendees not to walk out of the Black Rock Desert about 110 miles (177 kilometres) north of Reno as others had done throughout the weekend, including celebrity DJ Diplo and comedian Chris Rock. They didn’t specify why.

The festival had been closed to vehicles after more than a half-inch (1.3 centimetres) of rain fell Friday, causing flooding and foot-deep mud.

The road closures came just before the first of two ceremonial fires signaling an end to the festival was scheduled to begin Saturday night. The event traditionally culminates with the burning of a large wooden effigy shaped like a man and a wood temple structure during the final two nights, but the fires were postponed as authorities worked to reopen exit routes by the end of the Labour Day weekend.

Weather permitting, “the Man” is scheduled to be torched 9 pm Monday while the temple is set to go up in flames 8 pm Tuesday.

The National Weather Service in Reno said it should stay mostly clear and dry at the festival site Monday, although some light rain showers could pass through Tuesday morning. The event began August 27 and had been scheduled to end Monday morning, with attendees packing up and cleaning up after themselves.

“We are a little bit dirty and muddy, but spirits are high. The party still going,” said Scott London, a Southern California photographer, adding that the travel limitations offered “a view of Burning Man that a lot of us don’t get to see.”

The annual gathering, which launched on a San Francisco beach in 1986, attracts nearly 80,000 artists, musicians and activists for a mix of wilderness camping and avant-garde performances. Disruptions are part of the event’s recent history: dust storms forced organisers to temporarily close entrances to the festival in 2018, and the event was twice cancelled altogether during the pandemic.

At least one fatality has been reported, but organisers said the death of a man in his 40s wasn’t weather-related. The sheriff of nearby Pershing County said he was investigating but has not identified the man or a cause of death.

President Joe Biden told reporters in Delaware on Sunday that he was aware of the situation at Burning Man, including the death, and the White House was in touch with local authorities.

The event is remote on the best of days and emphasises self-sufficiency. Amid the flooding, revellers were urged to conserve their food and water, and most remained hunkered down at the site.

Some attendees, however, managed to walk several miles to the nearest town or catch a ride there.

Diplo, whose real name is Thomas Wesley Pentz, posted a video to Instagram on Saturday evening showing him and Rock riding in the back of a fan’s pickup truck. He said they had walked six miles through the mud before hitching a ride.

“I legit walked the side of the road for hours with my thumb out,” Diplo wrote.