HSBC Bank's head of foreign exchange cash trading has been arrested in New York on charges he traded ahead of his customers to make millions of dollars. 

Federal prosecutors in Brooklyn say 50-year-old Mark Johnson was arrested Tuesday night at Kennedy Airport. He was awaiting a court appearance Wednesday. 

U.S. Attorney Robert Capers says Johnson put personal and company profits ahead of his customers' needs. Johnson is a United Kingdom citizen and U.S. resident. 

His lawyer, Frank Kohl, didn't immediately respond to Bloomberg's request for comment.  

Assistant Attorney General Leslie Caldwell says Johnson and a co-defendant from the United Kingdom corruptly manipulated the foreign exchange market. 

Authorities say the men generated $8 million from a single 2011 transaction, some of it illegally. 

The bank isn't accused of any wrongdoing. HSBC declined CNBC's request for comment.