Swiss authorities say they are handing over to Brazil more than $120 million that were frozen as part of corruption probes involving state-run oil company Petrobras.

The federal prosecutor's office in Bern said Wednesday that it has opened nine investigations into alleged money laundering since last April, targeting eight Brazilian citizens along with "persons as yet unidentified."

It says it has found over 300 accounts in Switzerland that apparently were used to process bribes being investigated in Brazil. In total, it has frozen assets totaling about $400 million.

Prosecutors said they are returning part of the money to Brazil to signal Switzerland's "clear intention to take a stand against the misuse of its financial center for criminal purposes and to return funds of criminal origin to their rightful owners."