According to a Swiss prosecutor, about $4 billion may have been stolen from the Malaysian state-owned fund 1MDB.

The 1MDB fund was set up in 2009 to pay for major new economic and social developments in the country.

In 2015, Swiss authorities opened an investigation into 1MDB after it amassed more than $11 billion of debt.

Switzerland’s attorney general said on January 29 there were “serious indications that funds have been misappropriated from Malaysian state companies”.

Some of the money, the office of Michael Lauber said, had been transferred to Swiss accounts held by Malaysian former public officials and current and former public officials from the United Arab Emirates.

“To date, however, the Malaysian companies concerned have made no comment on the losses they are believed to have incurred,” the attorney general’s statement said.

Michael Lauber called on Malaysian authorities to give full judicial assistance to their Swiss counterparts.

A Swiss investigation into 1MDB was opened last year, citing “suspected corruption of public foreign officials, dishonest management of public interests and money laundering”.

In a statement on January 30, 1MDB said it “remains committed to fully co-operating with any lawful authority and investigation”, but had not yet heard from any foreign legal authorities.

Regulators in the US and Hong Kong are also reported to be investigating 1MDB.

The 1MDB’s advisory board is chaired by Malaysian PM Najib Razak, who launched the fund soon after taking office in 2009.

In July 2015, Malaysia’s then-Attorney General Abdul Gani Patail linked a donation of $681 million made to Najib Razak’s account with companies and bodies which had ties to 1MDB.

Abdul Gani Patail was replaced, and, after an investigation, his successor last week cleared Najib Razak of corruption saying that the money was a personal donation by the Saudi royal family to the prime minister’s private bank account.

“I am satisfied that there is no evidence to show that the donation was a form of gratification given corruptly,” said Attorney-General Mohamed Apandi Ali.

Most of the money was later returned, he said.

Malaysia’s anti-corruption commission said it would seek a review of the attorney-general’s decision.