FRANKFURT, Germany (AP) — German prosecutors say they have searched the Munich offices of investment firm BlackRock, which said it was cooperating in a probe of a tax scheme known as "cum-ex" transactions that has drawn the attention of law enforcers.

Prosecutors in Cologne said Wednesday they carried out the search Tuesday at the premises of BlackRock Asset Management Deutschland AG. BlackRock said in a statement that it was "fully cooperating with an ongoing investigation relating to cum ex transactions in the period 2007-2011."

The German nonprofit newsroom Correctiv coordinated an investigation by 19 media organizations that reported the transactions involved participants lending each other shares so they could collect reimbursement for tax they hadn't paid. The Correctiv report said the practice has cost European taxpayers 55 billion euros ($63 billion)