(Reuters) - Singer Neil Young, actor Mark Ruffalo and other celebrities on Thursday joined in calling for charges to be dropped against a documentary maker arrested while filming protesters who shut down oil pipelines from Canada to the United States, saying that she was acting as a journalist.

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Deia Schlosberg, producer of the 2016 documentary “How to Let Go of the World and Love All the Things Climate Can’t Change”, was taken into custody at a TransCanada Corp’s Keystone Pipeline site in Pembina County, North Dakota.

She was charged along with activists Samuel Jessup and Michael Foster on Thursday with three counts of conspiracy, charges which carry a maximum penalty of 45 years in prison.

Foster was also charged with trespassing and criminal mischief.

Oscar-nominated director Josh Fox, who produced “How to Let Go of the World” with Schlosberg, said in an open letter to President Barack Obama and North Dakota Governor Jack Dalrymple that the charges against her were “unfair, unjust and illegal.”

The letter was signed by more than 30 artists, filmmakers, writers and journalists, including Young, Ruffalo, actors Daryl Hannah and Frances Fisher and singer Alex Ebert of Edward Sharpe and the Magnetic Zeros.

“Journalism, especially documentary filmmaking, is not a crime, it’s a responsibility. The freedom of the press is a fundamental right in our free society. The charges filed against her are an injustice that must be dropped immediately,” said the letter, posted on the website EcoWatch.

The Pembina County Sheriff’s Office has repeatedly declined to comment and Pembina County State’s Attorney Ryan Bialas was not available to comment.

The criminal complaint accuses Schlosberg, 36, of agreeing with Jessup and Foster two weeks in advance to “engage in conduct that would constitute theft of property” and of traveling to the pipeline site in the same vehicle as Jessup and Foster.

All three appeared in court on Thursday morning for a bond hearing but remained in the Pembina County Jail several hours later. An attorney for Schlosberg could not immediately be reached for comment on Thursday.

Documentary filmmaker Lindsey Grayzel told Reuters that she was arrested in Washington state while filming the protests on Tuesday and her footage confiscated. She had not been charged as of Thursday afternoon.

During the protests, activists broke into valve stations at five remote locations to stop the flow of crude through arteries that pump around 15 percent of the oil consumed in the United States every day.

Companies operating the pipelines shut down their lines for between five and seven hours as a safety measure before restarting them, according to Reuters estimates and company representatives.

The action on Tuesday underscored the vulnerability of the thousands of miles of pipeline in the United States that deliver energy to consumers.

Together, the pipelines have the ability to carry nearly 2.8 million barrels a day of crude across the Canada-U.S. border.

On Monday, actress Shailene Woodley and 26 other people were arrested on charges of trespassing and engaging in a riot at a demonstration against the Dakota Access Pipeline near St. Anthony, North Dakota.[nL1N1CG1CU]