After an inquiry, Oracle Racing and Ben Ainslie Racing were found to have used illegally modified boats in America’s Cup World Series races held between June 2012 and last April.

The AC45s that were used to race are a class of 45-foot training yachts used in previous world circuit regattas, and they have not raced since Naples in April. They are distinct from the AC72 yachts (72-footers) that are being raced in this year’s Louis Vuitton Cup and the America’s Cup.

The issue came to light when the AC45 fleet was being prepared for the Red Bull Youth America’s Cup event. It was reported that one of the forward kingposts on one of the boats seemed unusually heavy.

Inspection by the measurement committee discovered that it was filled with “a resin/ballast slurry of some type.” Further investigation revealed that the other two Oracle AC45s had received similar modifications, in their case bags of lead shot in the kingpost.

Oracle Racing said it will return the trophies the teams won and it issued a statement that said, in part, “The withdrawal is in spite of the fact that the modifications had no impact on the performance of the boats.

“Our team is very disappointed by this turn of events, and I believe that voluntarily withdrawing from these past AC45 regattas is the appropriate corrective action,” Oracle Racing CEO Russell Coutts said in the statement. “Going forward, we remain focused on our AC72 training in preparation for the upcoming America’s Cup this September.”

Click here for the report by Yachting World.