Former Vice President Joe Biden released his $1.7 trillion climate plan online Tuesday — and it had to be updated after reports that parts of the proposal appeared to have been taken from other sources.

Several sentences in Biden's lengthy "Plan for a Clean Energy Revolution and Environmental Justice" were taken directly from two environmental groups without attribution — an embarrassment for a candidate who's faced plagiarism allegations in the past.

Two of the similar lines were first flagged on Twitter by Josh Nelson, vice-president of CREDO mobile, a progressive company. "The paragraph in Joe Biden’s climate plan about carbon capture and sequestration includes language that is remarkably similar to items published previously by the Blue Green Alliance and the Carbon Capture Coalition," Nelson wrote.

On the left, Joe Biden’s climate plan. Source: https://t.co/WHWvRK784s



On the right, a description of the Carbon Capture Coalition on the Center for Climate and Energy Solutions website. Source: https://t.co/nulmTqXZ1p pic.twitter.com/4f010MqNjY — Josh Nelson (@josh_nelson) June 4, 2019

Nelson told NBC News he'd googled some of the lines from the Biden plan because "it did not strike me as language that would have come from a presidential campaign." The longtime environmental activist and writer said other lines "seemed familiar."

The conservative website the Daily Caller then reviewed the plan, and found three other instances of language that was similar to other published material.

"The average American sewage pipe is 33 years old, with many pipes dating back 50 or even 100 years," the Biden plan said — a word for word copy of a line from nonprofit American Rivers.

The Biden campaign updated the plan to add the proper attribution to the flagged lines soon after the Daily Caller report.

"Several citations, some from sources cited in other parts of the plan, were inadvertently left out of the final version of the 22-page document. As soon as we were made aware of it, we updated to include the proper citations," the campaign said in a statement.

President Donald Trump criticized Biden over the climate plan changes, but added that the media would be sympathetic to him.

Plagiarism charge against Sleepy Joe Biden on his ridiculous Climate Change Plan is a big problem, but the Corrupt Media will save him. His other problem is that he is drawing flies, not people, to his Rallies. Nobody is showing up, I mean nobody. You can’t win without people! — Donald J. Trump (@realDonaldTrump) June 5, 2019

Biden's first campaign for president in the 1988 race was derailed after he was accused of plagiarizing parts of a speech from a British politician in the Democratic debate. The then-Delaware senator said afterward it was a mistake and noted he'd attributed the speech correctly on the campaign trail, but he was then hit by reports he'd plagiarized in an article while in law school in 1965.

Biden had to send a letter to the Syracuse University College of Law faculty pleading not to be expelled, The New York Times reported. "My intent was not to deceive anyone," Biden reportedly wrote, explaining he had misunderstood footnoting rules. "For if it were, I would not have been so blatant."

CORRECTION (June 5, 2019, 6:05 a.m. ET): A previous version of this article misstated the law school that Joe Biden attended. It was the Syracuse University College of Law, not the Fordham University School of Law.