(Bloomberg) -- German prosecutors raided the Frankfurt offices of Morgan Stanley as part of their probe into the controversial Cum-Ex trades, a person familiar with the matter said.

The search started early on Tuesday according to the person who asked not to be identified because the matter is private. A spokesman for Cologne prosecutors confirmed a raid is taking place in Frankfurt but declined to identify the target. 

Authorities are searching a bank the homes of two suspects in a probe over Cum-Ex and related strategies. More than 75 officers are taking part in the action, he said.

Morgan Stanley’s press office didn’t immediately respond to a call and email requesting for comment.

Cologne prosecutors, who are probing about 1,500 people from the financial industry, are ramping up the pressure on international banks in their. They raided Barclays Plc’s Frankfurt offices in March just one week after Bank of America Corp.’s Merrill Lynch premises were hit. 

Cum-Ex was a trading strategy that siphoned off at least 10 billion euros ($10.5 billion) in government revenue. Named for the Latin term for “With-Without,” Cum-Ex took advantage of German tax laws that seemed to allow multiple investors to claim refunds of a tax on dividends that was paid only once. The nation moved to abolish the practice in 2012.

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