(Reuters) — Switzerland's top court this month ruled against a freeze on $900 million belonging to a jailed Angolan businessman, citing insufficient evidence for money laundering alleged by prosecutors.

The ruling reverses one of the largest personal asset freezes in Swiss history, levied by prosecutors in 2018 and upheld by a court last year, but keeps it in place pending appeals.

Carlos Manuel de Sao Vicente was a key figure in Angola's oil industry, heading a group of companies called AAA International, which sold insurance contracts to state oil company Sonangol over nearly two decades of bumper profits.

According to a copy of the unpublished March 10 decision obtained by Reuters, the Supreme Court in Lausanne noted that prosecutors “did not precisely determine, as it was their task to do, the predicate offenses for money laundering necessary to justify the upholding of a seizure on the bank assets of the appellant.”

“The appellant has given explanations for each of the (bank) activities deemed problematic by the public prosecutor,” the court added.

The Swiss public prosecutor did not immediately respond to a Reuters request for comment on the court’s ruling.

Prosecutors said in the original court filing they had frozen $1.25 billion in accounts associated with Mr. de Sao Vicente, his family and companies after Swiss banks flagged transfers to them as suspicious.

They released most of the accounts in April 2019 save for two that were in Mr. de Sao Vicente's name.

Mr. de Sao Vicente, who has been jailed on suspicion of corruption in Angola since late last year, has described the transfers between 2012 to 2019 as legitimate reimbursement for loans he had made earlier.

Angolan prosecutors did not respond to a Reuters request for comment on the ruling. Court filings to date suggest there has been no request by Angola for a repatriation of funds.

Lawyers for de Sao Vicente's company AAA International told Reuters the ruling vindicates him as a legitimate businessman and that they expect the freeze to eventually be lifted.

“The decision clearly demonstrates that the Swiss case is empty and it will be much more difficult for the Swiss prosecution service to maintain the seizure,” Sonja Maeder Morvan of Geneva-based Reiser Avocats told Reuters.

Angola, which draws a third of state revenues from oil, is seeking to defy decades of perceived corruption and nepotism as it seeks to attract foreign investment to its flagging economy.