DENVER (AP) -- Lawyers for the American Civil Liberties Union say Weld County authorities went on a "fishing expedition" when they seized thousands of tax documents of suspected illegal immigrants in an identity theft investigation.

The ACLU said in a brief filed with the Colorado Supreme Court that the judges should uphold an April ruling by a lower court that stopped the investigation.

The brief was filed Friday.

The sheriff and district attorney said in their appeal last month they had substantial evidence that hundreds of illegal immigrants were stealing identities to file taxes through a tax preparer in Greeley.

Authorities filed identity theft and criminal impersonation charges against more than 70 people before the investigation was stopped.

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