Leonardo DiCaprio is aiding the investigation into a Malaysian embezzlement scam linked to his hit film The Wolf of Wall Street, according to his spokesperson on Tuesday.

The Hollywood star contacted the US justice department in July just after it filed a lawsuit to seize more than US$1bn in allegedly ill-gotten assets tied to Malaysian state investment fund 1MDB, including rights to the film, DiCaprio’s spokesperson said.

Allegations of a vast international scheme of embezzlement and money-laundering involving billions of dollars of 1MDB money began to emerge two years ago, rocking Malaysia’s political establishment.

The statement says DiCaprio is awaiting direction from the US justice department regarding any funds that may have supported his environmental foundation or 2013 film The Wolf of Wall Street.

The Oscar-winning actor released a statement through his representatives on Tuesday saying he will return any gifts or donations connected to the Malaysian wealth fund, pending a fraud investigation of that fund by the US and other countries.

“Both Mr DiCaprio and [the Leonardo DiCaprio Foundation] continue to be entirely supportive of all efforts to assure that justice is done in this matter,” the statement said. “Mr DiCaprio is grateful for the lead and instruction of the government on how to accomplish this.”

The US justice department says that at least US$3.5bn has been stolen from 1MDB by people close to Malaysian prime minister Najib Razak.

Najib created the fund in 2009, shortly after he took office, to promote economic development projects in the Asian nation, but the fund accumulated billions in debts over the years.

The US justice department has initiated action to seize US$1.3bn it says was taken from the fund to buy assets in the US, including luxury properties in New York and California, a US$35m jet, art by Vincent Van Gogh and Claude Monet, and financing of The Wolf of Wall Street, according to federal government complaints filed in Los Angeles in July.

The government complaints also say that more than US$700m has landed in the accounts of “Malaysian Official 1”. They did not name the official, but appear to be referring to Najib.

Leonardo DiCaprio in The Wolf of Wall Street. Photograph: Allstar/Paramount Pictures

The US justice department complaints do not mention DiCaprio by name, but make an oblique reference to “Hollywood Actor 1”, who during his Golden Globe acceptance speech thanked “the entire production team” and singled out several people close to Najib and implicated in the scandal as “collaborators” on the film.

DiCaprio won the Golden Globe in 2014 for his Wolf of Wall Street performance. The US justice department complaints identify the film’s “collaborators” by name, including Najib’s stepson, Riza Shahriz Abdul Aziz, who co-founded movie production company Red Granite Pictures. Besides The Wolf of Wall Street, other films produced by Red Granite include 2015’s Daddy’s Home and 2014’s Dumb and Dumber To.

DiCaprio reportedly was friends with Aziz associate Jho Low, also named in the lawsuit.

Last week, a Swiss rainforest charity demanded that DiCaprio resign from his post as a United Nations messenger of peace if he does not disclose his financial ties to the Malaysian fund. But on Monday, a UN spokesman expressed continued support for the actor.

Stephane Dujarric said he understands that DiCaprio’s foundation is working with the relevant authorities in the US to resolve the issue.

“We continue to welcome his public work on behalf of climate change,” Dujarric said.

The Bruno Manser Fund, a Swiss NGO campaigning against corruption in Malaysia, said it welcomed DiCaprio’s announcement but called on the actor to fully disclose his financial ties to Low, Aziz and Red Granite Pictures.

“DiCaprio’s public statement leaves key questions open,” said Lukas Straumann, the executive director of the Bruno Manser Fund. “How much money did Leonardo DiCaprio and his foundation get from politically exposed persons from Malaysia and why didn’t he conduct due diligence upon receiving these funds?”

The organization also questioned whether DiCaprio would pay back the estimated US$25 million he received for his role in The Wolf of Wall Street.

“While we appreciate the statement and his cooperation with the department of justice, there is clearly more DiCaprio could do to end this disgraceful chapter in Hollywood history,” the statement said.

Najib has consistently denied any wrongdoing since allegations of massive fraud in the fund erupted last year. He remains firmly in political control by clamping down on critics and because of unwavering support of most ruling party members.

Democracy group Bersih plans to hold a mass street rally on 19 November to demand Najib’s immediate resignation to allow an independent investigation in Malaysia into the financial scandal.

Associated Press and Agence France-Presse contributed to this report.