NEW YORK – The companies that determine Americans’ credit scores are about to come under government oversight for the first time.

The Consumer Financial Protection Bureau said Monday that it will start supervising the 30 largest firms that make up 94 percent of the industry. That includes the three big credit reporting firms: Equifax Inc., Experian and TransUnion.

Each of the three major credit reporting agencies maintains files on more than 200 million Americans.

In remarks prepared for a speech Monday, Richard Cordray, the government agency’s director, said that scorekeeping by credit bureaus plays such a large role in Americans’ financial lives, it requires scrutiny.

The bureau said its oversight may include on-site examinations, and that it may require credit bureaus to file reports.

“It’s a wonderful thing for the American public,” said Pamela Banks, the senior policy counsel for Consumers Union, the policy arm of Consumer Reports. “Now there’s somebody on their side.”

Banks said she expects that when people dispute details on their credit reports, credit bureaus will now act more quickly to fix any problems. “They won’t want the CFPB breathing down their necks,” she said.

The announcement Monday wasn’t a total surprise, according to industry observers, because the bureau had hinted earlier this year that it was considering supervising the industry.

Gerry Tschopp, a spokesman for Experian, said the government already oversees the industry, because the Federal Trade Commission has been responsible for enforcing the Fair Credit Reporting Act since it became law in 1970.

Tschopp said he had “no concerns” about the agency’s oversight. A statement from Experian said the company and the bureau share the goal of helping consumers get “access to fair and affordable credit.”

The protection bureau will start regulating the industry after the new rule takes effect Sept. 30.