Three South Florida law firms that represent mortgage lenders are being investigated by the state attorney general over allegations they forged documents filed with the courts in foreclosure cases.

The Florida attorney general issued the subpoenas this week, requesting reams of paperwork by the end of the month from attorneys working in the foreclosure capital of the country.

The investigation targets firms considered to be handling the largest number of foreclosures in Florida on behalf of lenders, in some cases handling thousands of cases a month. They are the Law Offices of David J. Stern in Plantation; the Law Offices of Marshall C. Watson in Fort Lauderdale; and Shapiro & Fishman, which has offices in Boca Raton and Tampa.

The subpoenas request documents going back to at least Jan. 1, 2008.

Attorney General Bill McCollum said the firms may have presented fabricated documents in court to obtain foreclosure judgments against homeowners. Thousands of final judgments of foreclosure against Florida homeowners may have been the result of improper actions by the firms under investigation, said McCollum, a Republican who is a running for governor.

He likened their work processing so many foreclosures to a mill, churning out foreclosures in large volumes.