Tourists on a commercial snowmobile broke park rules by driving too close to Yellowstone National Park's iconic Old Faithful geyser yesterday at a time when most staff were off work during the partial US government shutdown.

In an interview today, park Superintendent Dan Wenk said one of the concession operators who is authorised to conduct snowmobile tours through Yellowstone - and was allowed to continue doing so even as most park employees stopped work this weekend - violated park rules.

"This guide told two of his clients that they could drive around the visitor centre and into an area where the snowmobiles are prohibited," Wenk said, adding that staff members spotted the activity on the park's webcam and issued a citation to the guide, who now faces a mandatory court appearance.

In light of the incident, Wenk said, park officials were holding a conference call with all concession operators to remind them: "All laws, regulations and policies are still being enforced at Yellowstone National Park."


He said the geyser and its immediate surroundings did not appear to have been damaged. Some unauthorised, noncommercially operated snowmobiles also tried to enter the park during the past few days, but "we've been able to turn those around," Wenk said.

The incident at Yellowstone came after Interior Secretary Ryan Zinke directed his deputies to make public lands as accessible as possible during the government shutdown, part of an administration strategy to reduce the public impact of the political impasse.

Speaking to reporters, Zinke said he wanted to preserve access to national parks and monuments even if there was reduced staffing for a period of time.

"The public lands are for the public," he said. "They're not for special interests."

Trump officials were particularly focused on keeping the federal government's most visible operations, such as national parks, running. Office of Management and Budget General Counsel Mark Paoletta sent an email to deputy secretaries and general counsels across the government suggesting they use carryover funds "to minimise the shutdown's disruption," according to a copy of the message obtained by the Washington Post.

"If your agency expects that one of its public-facing programmes or services will experience a significant disruption due to the lapse in appropriations, please consult your Office of General Counsel (OGC) to consider carefully the legal necessity of ceasing key services and to evaluate alternatives, consistent with the law, that will minimise the impact of this unfortunate situation," Paoletta wrote.

Some conservationists said the shutdown, which ended today after Congress passed and President Donald Trump signed a short-term funding bill to reopen the government, highlighted the risks associated with the Trump Administration's strategy.

"Looting and damaging recreational use were at the top of our concerns when you don't have park rangers and staff on the ground," said Kristen Brengel, vice-president of government affairs for the National Parks Conservation Association (NPCA). "So it's really disappointing that it actually happened, but it also says why we need staff there."

Yellowstone was not the only national park to experience unauthorised activities over the weekend during the partial shutdown .

At Pennsylvania's Gettysburg National Military Park, a family with metal detectors and a drone - both of which are prohibited there - entered the park over the weekend. Rangers intercepted them and used it as "an educational opportunity," National Park Service spokesman Jeremy Barnum said. Authorities let the family go without a citation. They did not damage the park's resources, Barnum added.

Shane Farnor, an online advocacy manager at NPCA, said that during a weekend visit to California's Joshua Tree National Park, he saw dogs roaming without leashes and running on trails where they are not allowed. Dogs must be leashed in the park.