GREELEY, Colo. -- Weld County authorities are investigating the alleged use of stolen or phony Social Security numbers by suspected illegal immigrants to file for $2.6 million in tax deductions they're not owed.

Weld County District Attorney Ken Buck said that roughly 1,300 clients of the tax business, Amalia's Translation and Tax Service, in Greeley may have used stolen or phony Social Security numbers. The investigation began in August, when Weld County deputies received information regarding an identity theft occurring in the county.

In October, deputies searched through nearly 5,000 tax files and discovered 1,338 suspected cases of identity theft or criminal impersonation on tax returns file din 2006 or 2007.

“This investigation has revealed so many issues on so many levels,” said Weld County District Attorney Ken Buck. “The most disturbing of which is the vast number of American citizens who have had their identity stolen. As an office, we file approximately 2,500 criminal cases a year. From one tax preparer in one town, we have increased that amount by more than 50%.”

Authorities say 11 suspected illegal immigrants have been arrested. The arrests stem from an investigation that began three months ago after a Texas man was audited by the IRS for underreporting his Colorado income. His Social Security number was stolen and used to file for tax refunds.