Oracle Team USA, the defending America's Cup champion, is being investigated by the regatta's International Jury for alleged illegal modifications the team made to its boats during exhibition races in 2012 and earlier this year.
Oracle has been ordered to return the trophies that the team won in the America's Cup World Series races, which took place in San Francisco and Rhode Island last year and in Italy this past April.
The jury is investigating a report that the team's three AC45 boats had additional weight in the forward king posts of the vessels in violation of race rules.
The modifications were recently discovered during inspections of the boats for the upcoming Red Bull Youth America's Cup.
The report, written by the regatta's Measurement Committee, concluded that the modifications "appear to be intentional efforts to circumvent the limitations of the AC45 class rule, and are therefore serious in nature.
"The jury wrote on Thursday that it is investigating the incident under Rule 69, which covers "allegations of gross misconduct."
The rules stipulate that the jury can ban a person or boat from future races if it finds misconduct was committed.
Oracle Team USA CEO Russell Coutts wrote in an email to the jury that he "had no knowledge whatsoever that the boat was being raced out of measurement. I am deeply disappointed by this incident and will do all I can to assist the relevant parties in any future investigations."
Oracle Team USA has retroactively withdrawn from the events, Coutts wrote.
The team says that the modifications had no impact on race
performances and were made by a small number of team members without the knowledge of management or the team's skippers.
The 45-foot boats are separate from the 72-foot vessels being used in the Louis Vuitton Cup currently under way to decide who will face Oracle in the America's Cup Finals next month.
Leaders of Emirates Team New Zealand, the favorites to win the Louis Vuitton Cup and take on the American team, expressed surprise at the revelations regarding their opponents.
Emirates Team New Zealand managing director Grant Dalton said in a statement, "I find it difficult to believe that what we learned ... actually happened at the top level of our sport."
The New Zealand team is facing Luna Rossa Challenge, an Italian team, in the finals of the Louis Vuitton Cup starting this Saturday.
The investigation into the Oracle team is the latest challenge in what has been a troubled run for the America's Cup races in San Francisco.
Artemis Racing, a Sweden-based team, had a sailor die when the team's boat capsized during a practice run in May, prompting new safety reforms to be implemented for the races.
There were also only three challengers vying to compete against Oracle for the America's Cup -- far fewer than regatta organizers had initially anticipated. The downsizing has been coupled with struggles to raise enough funds to repay the city for costs related to the races.