Vienna  - Austrian banker Julius Meinl V was released Friday after posting bail worth 100 million euros (133 million dollars). However, he remains a key suspect in a large investment fraud case involving his family's Meinl Bank AG.

The head of one of Austria's most established business dynasties drove away from the Vienna prison where he had spent two nights without talking to journalists, according to Austrian press agency APA.

Meinl, 49, was taken into custody Wednesday on suspicion of fraud and breach of trust over fund share certificates issued by Meinl European Land (MEL), a real-estate portfolio set up by the bank formerly led by Meinl.

Up to 150,000 investors have seen their shares lose some 75 per cent of their value since 2002, when MEL went public.

House searches conducted in Bratislava unearthed evidence that indicated that Meinl, who currently serves as chairman of Meinl Bank's supervisory board, was involved in MEL's operations, according to media reports.

Austrian authorities are investigating massive share buy-backs apparently conducted to prop up MEL shares, as well as inflated fees that Meinl Bank charged MEL.

Jersey-based MEL was sold to the Citibank group and Israeli investor Gazit Globe Ltd last year and was renamed Atrium European Real Estate Ltd. dpa