BOSTON (REUTERS) - Citigroup Inc was fined US$30 million (S$37.5 million) by Massachusetts' top securities regulator after an analyst sent unpublished and confidential research about a technology company to institutional clients, including Steven A. Cohen hedge fund SAC Capital Advisors, officials said on Thursday.

William Galvin, Massachusetts' Secretary of the Commonwealth, said Citigroup analyst Kevin Chang sent research about Hon Hai Precision Industry Co, a major supplier of Apple Inc iPhones, to SAC, T. Rowe Price , Citadel and GLG Partners.

The fine comes at a critical time for Cohen's US$14 billion hedge fund, which faces criminal insider trading charges. The Stamford, Connecticut-based firm has said it has done nothing wrong.

Galvin's office said three Citigroup clients traded in Apple stock between the time it received Chang's information and the day his report was official published.

"Due to Kevin Chang's release of his research views prior to publication, he had to publish his research report early, but not before his revised Apple iPhone production estimates were communicated to the four clients," Galvin said in a statement.

The Hon Hai research report contained significant cuts in Apple iPhone production numbers and would have a detrimental impact on Apple, the regulator said.

A Citi spokesman said the bank takes "regulatory compliance requirements very seriously and train all of our employees about these obligations. We are also constantly working to improve, manage and monitor the compliance and controls process".