(CNN) — Known more for tweeting lovely pictures of Yosemite, Yellowstone and other national parks, the US National Park Service's social media presence has taken a turn for the subversive in the age of Trump.

A Twitter account that claims to be run by park service employees on their own time published a tweet going after newly inaugurated President Donald Trump.

"Can't wait for President Trump to call us FAKE NEWS," tweeted @AltNatParkSer on Tuesday. "You can take our official twitter, but you'll never take our free time."

The account had more than 990,000 followers as of Thursday morning, and it's rising. (The official National Park Service account, @NatlParkService , has 381,000 followers.)

While CNN could not confirm who created and operates the account, the Twitter bio states that the group is the park service's "unofficial resistance" team.

In a series of tweets on Thursday morning, posters claiming to be part of the group's launch said they had taken over running the site, "advocating scientific and environmental interests."

"Several of us are environmental activists and two are journalists [our FACT checkers]. All of us are former scientists," they tweeted.

The original posters claimed to be based at Mount Rainier National Park in Washington state -- although they spelled the name of the park incorrectly in their tweet. The account now claims to be based in New York, Edinburgh and Hong Kong.

The account has occasionally used the Canadian/British spelling of a few words, Twitter user @NickKramarev noted.

The park service, which declined to comment on the @AltNatParkSer account, is better known for tweeting out pictures of stunning vistas, wild animals and warnings about road closings in winter than getting involved in presidential politics.

The latest Twitter spat started when the park service retweeted messages that negatively compared the crowd sizes at Donald Trump's inauguration on Friday to those at Barack Obama's in 2009.

Representatives from the new administration asked the digital team at the Interior Department, which oversees the park service, to temporarily stop using Twitter. The agency claims the decision was out of a concern that the account was hacked.

That was followed by tweets on Tuesday about climate change from Badlands National Park, which is located in South Dakota and had only 7,000 Twitter followers on Monday. The park now has more than 215,000 followers since publication, a number that continues to rise.

The climate change tweets have been deleted , but a Tuesday tweet of a goat and kid pictured overlooking a cliff remains, with the words "CAPTION THIS!"

The account had been overtaken by a former employee who still had the Twitter password, the park said.

White House not responsible, spokesman says

White House spokesman Sean Spicer said that the White House had not ordered that the tweets be deleted nor had White House officials issued a larger mandate shutting down speech at federal agencies.

"I know in the park service, for example, over the weekend, somebody, an unauthorized user, had an old password in the San Francisco office, went in and started retweeting inappropriate things that were in violation of their policy," Spicer said at his Wednesday press briefing.

Another unofficial Badlands account was created this month, still trolling Trump.

"Fun Fact: Badlands NP today is home to 39 mammal species! (As part of budget restructuring, that number will be reduced by half by 2019.)" the account tweeted out Wednesday.

While some posts from the unofficial @AltNatParkSer Twitter handle, which was first created in May 2015, are jokes and retweets of fans' pretty park pictures, some are not.

"This is the National Park Service's Cultural Resources Climate Change Strategy. Pls download before it is removed," the account tweeted on Tuesday. A link to the report is included in the tweet.

If the Twitter users are government employees, they could be found in violation of their department's social media policy, says social media strategist Peg Fitzpatrick. The Interior Department social media policy bans the sharing of non-public information or sharing it only through third-party sites.

Still, adds Fitzpatrick, "I don't know how they could monitor all the government employees."

Expect social media debate to continue

Expect more debate about the Trump Administration's policies on social media, despite any threats.

"They can certainly try to muzzle employees and threaten them and make them afraid," says Trevor Trimm, co-founder and the executive director of the Freedom of the Press Foundation.

"But we are talking about literally hundreds of thousands or millions of people who work in federal agencies, and they are quickly going to get fed up, especially when the administration isn't using secrecy to prevent any important secret from getting out. Instead they're trying to censor scientific facts."

It's more likely that the Trump Administration will take another tactic, journalism lecturer Lina Dencik, of the UK's Cardiff University, tells CNN.

Faced with facts or opinions they find objectionable, "they will try to drown it out, to make it not clear cut," Dencik says.

"We didn't really use to see how easy it was to provide false information," says Dencik, who focuses on the role of new media technologies in modern activism and protest movements.

"But we are becoming more literate around it. People will have to become more aware of what they're reading and where it's coming from. That's going to take a long time."

In the meantime, US futurist and author Amy Webb predicts that "we're going to be on this massive adrenaline and endorphin rush for the next couple years" as these types of debates play out on social media.