Countrywide Financial Corp., the largest American mortgage lender, is under investigation by the Federal Bureau of Investigation for possible securities fraud, according to a person familiar with the probe.

Investigators are focusing on whether Countrywide officials misrepresented the company’s financial position and the quality of its mortgage loans in securities filings, the person, who declined to be identified because he wasn’t authorized to speak about the probe, said Saturday. He described the inquiry, reported earlier by the Wall Street Journal, as preliminary.

Countrywide is among at least 14 companies that the FBI is checking for possible accounting violations related to the subprime lending crisis, including mortgage lenders, housing developers, and Wall Street firms that package loans as securities. The FBI announced the review in January without identifying any of the companies.

“There’s a whole lot of excitement and hullabaloo, but proving criminal conduct is likely to be difficult,” the president of Mortgage Banking Solutions, an Austin, Texas consulting firm, David Lykken, said Saturday.

“A lot of people were caught up in the atmosphere when the housing market was booming.”