A billion-dollar Singapore money laundering probe is shining a light on fund flows from abroad and raising questions about loopholes that enabled an alleged crime syndicate to accumulate luxury property, Bentley cars and cryptocurrency.

The investigation erupted into public view in mid-August after police arrested 10 foreigners — most originating from China — and accused them of laundering criminal proceeds. It’s prompted questions about whether the banking giants that drive the economy have done enough to block dubious transactions.