BOSTON (AP) — The credit card data theft that affected about 300 people who attended conventions in Boston this fall is more widespread than initially thought, a police detective investigating the breach says.

The thefts were not limited to people who attended conferences at the Boston Convention & Exhibition Center, and extend through other areas of the city, Detective Steven Blair said.

Based on initial interviews with credit card companies, the tally of victims could be "hundreds" more than those who already have reported unauthorized or fraudulent charges on their credit cards, he told The Boston Globe (http://b.globe.com/1dsMREE ) for a story Thursday.

"It's extensive," Blair said. "It's not just focused on the Seaport area," where the convention center is located.

About 300 people from two conferences — the American Society of Human Genetics meeting in October and the American Public Health Association gathering in November — told organizers their credit cards had been compromised and used for fraudulent purchases around the country and even overseas.

Officials with the state agency that runs the convention center have said they are not the source of the breach, and that several employees have been victimized.

Some area hotels and restaurants also have denied responsibility.

Blair said the scope of the crime suggests the thieves hacked into the computer system of a business or businesses and captured the data that way.

"Somebody's computer got compromised," he said. "It's not one individual working at a restaurant skimming."

In addition to the Boston police probe, the thefts are being investigated by the state attorney general's office and the U.S. Secret Service.

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Information from: The Boston Globe, http://www.bostonglobe.com