Tourists on a commercial snowmobile broke park rules by driving too close to Yellowstone National Park’s iconic Old Faithful geyser Sunday, park officials confirmed, at a time when most staff was furloughed during the partial government shutdown.

In an interview Monday, park superintendent Dan Wenk said that one of the concession operators that is authorized 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.

“His guide told two of his clients that they could drive around the visitor center and into an area where the snowmobiles are prohibited,” Wenk said, adding that staffers 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 Monday 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 unauthorized, non - commercially operated snowmobiles also tried to enter the park over the past few days, Wenk said, but “we’ve been able to turn those around.”

Yellowstone is not the only national park to have experienced illegal activities since Interior Secretary Ryan Zinke directed his deputies to make public lands as accessible as possible during the partial shutdown.

At Pennsylvania’s Gettysburg National Military Park, a family with metal detectors and a drone — both of which are prohibited — entered the park over the weekend. Rangers intercepted them and used it as “an educational opportunity” said NPS spokesman Jeremy Barnum in a phone interview, and let them go without a citation. They did not damage the park’s resources, Barnum added,

And Shane Farnor, an online advocacy manager for the National Parks Conservation Association (NPCA), said in an interview that during a weekend visit to California’s Joshua Tree National Park, he saw dogs roaming without leashes, which isn’t allowed, and running on trails where they’re not allowed.

Speaking to reporters Monday, Zinke said he wanted to preserve access 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 have been particularly focused on keeping the federal government’s most visible operations, such as national parks, running during the budget impasse. Office of Management and Budget General Counsel Mark Paoletta sent an email Saturday evening, obtained by The Washington Post, to deputy secretaries and general counsels across the government suggesting that they use carry-over funds “to minimize the shutdown’s disruption.”

“If your agency expects that one of its public-facing programs or services will experience a significant disruption due to the lapse in appropriations,” Paoletta wrote, “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 minimize the impact of this unfortunate situation.”

But some conservationists said that the shutdown, which could end soon now that senators have reached a bipartisan compromise 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, NPCA’s vice president of government affairs. “So it’s really disappointing that it actually happened, but it also says why we need staff there.”

While critics questioned whether leaving public lands understaffed made them temporarily vulnerable, at least someone had stepped in to look for asteroids that could potentially collide with the Earth.

The staff of NASA’s Planetary Defense Coordination Office, which is responsible for monitoring asteroids and comets that could collide with Earth, was also furloughed starting Saturday.