A bounced check for $40 tipped off a Chicago law firm to a trusted employee's scheme that, over nearly seven years, drained more than $880,000 from the firm's bank account, Cook County prosecutors said Wednesday.

Joan M. Sanchez, 52, 10445 Linder Ave., Oak Lawn, spent nearly $48,000 of the stolen money on lunches, State's Attorney Anita Alvarez said.

Sanchez had spent 24 years with the downtown firm of Kelly Olson Michod Dehann & Richter, including 21 years as office manager.

"It's a terrible breach of trust," said Stephen Cohen, an attorney with the firm.

Chicago police arrested Sanchez on Tuesday at her home, and Circuit Judge Maria Kuriakos-Ciesil set bail Wednesday at $100,000.

Alvarez said the thefts began in October 2002 and continued through April 2009. During that time, Sanchez wrote 234 unauthorized checks from the firm's business account, Alvarez said.

She said Sanchez forged the signature of one of the firm's partners on the checks, created fake entries in the firm's ledger to make it look as though the checks were issued to legitimate vendors and then voided the checks.

Prosecutors allege that Sanchez wrote 176 checks, totaling $836,500 and made payable to herself, and deposited them in her personal checking account at a Chicago bank.

Another 58 checks totaling $47,799 were written by Sanchez and made payable to a lunch club at the Chicago Mercantile Exchange, where she often dined with her mother, Alvarez said.

The scheme came to light while Sanchez was vacationing in Hawaii and a $40 reimbursement check drawn on the firm's bank account bounced, even though the ledger showed ample funds in the account, prosecutors said.

Cohen said the firm had little to say about the matter.

"The matter is in the hands of the state's attorney, and our position is they're handling it, and we don't want to do anything to jeopardize their case," he said.