When Joe Biden s presidential campaign released his ambitious climate change plan Tuesday, it landed almost immediately with accusations of plagiarism.

Josh Nelson, vice president of CREDO mobile, a phone company based in San Francisco that raises money for progressive organizations, first highlighted instances of plagiarism Tuesday morning on Twitter.

Reports by Business Insider and conservative news site The Daily Caller found other instances of plagiarism, in which Bidens 2020 Democratic presidential campaign uses phrasing that is identical or nearly identical to literature by other organizations.

In response to the allegations, the Biden campaign told HuffPost it had inadvertently left out several citations in the final version of the climate plan and have since updated the campaign website to include those sources.

Nelson revealed two instances where the former vice presidents plan, which was published to his campaign site early Tuesday, included sentences identical to material from two environmental organizations: Blue Green Alliance and the Carbon Capture Coalitions Center for Climate and Energy Solutions (C2ES).

Bidens plan appeared to have lifted a sentence from the Blue Green Alliances 2017 letter to the Senate Environment and Public Works Committee and the C2ES website.

Business Insiders report Tuesday also said that Bidens climate plan pulled a phrase from the website of an advocacy group known as American Rivers.

The infrastructure portion of American Rivers website notes that the average American sewage pipe is 33 years old, with many pipes dating back 50 or even 100 years. Bidens plan used the same language.

The Daily Callers report showed Bidens campaign used reporting on pollution caused by air travel from news site Vox in its plan, with similar sentence structures, without citing Vox .

Biden is no stranger to plagiarism scandals. During his 1988 presidential campaign, when he was still a senator from Delaware, Biden admitted that he copied a speech from a British politician without attributing it to him. He also admitted to plagiarism in an article he wrote during his first year in law school, The New York Times reported at the time.

He eventually withdrew his 1988 presidential campaign .

Matt Bruenig, the founder of the liberal think tank Peoples Policy Project, defended the uncited passages in Bidens climate plan, suggesting that presidential candidates often use available policy materials when crafting policies on which they will run their campaigns.

Bidens campaign said Tuesday that it had updated the plan after learning of the plagiarism accusations.

Several citations were inadvertently left out of the final version of the 22-page document, the campaign said. As soon as we were made aware of it, we updated to include the proper citations.

While Bidens website was updated with citations, the portion of his climate plan that appears similar to Voxs report still does not cite the news site.