An Administration for Children’s Services office worker who routinely worked with a safe full of checks bilked banks out of more than $600,000, the city said yesterday.

Darly Estinval, 37, pleaded guilty in Brooklyn federal court to bank-fraud conspiracy in the three-year-old scheme.

Her job, mailing the checks to vendors, gave her access to the safe.

Estinval, who worked at ACS from 2004 to 2008, faces 33 to 41 months in prison.