Personal data from hundreds of Massachusetts employees of the pet care retailer Petco Animal Supplies Inc. were compromised due to a computer theft that occurred in May, according to the company.

According to a report filed in late July with the Massachusetts Office of Consumer Affairs and Business Regulation, five laptop computers were stolen from an outside firm that Petco, which is based in San Diego, had hired to audit the company’s 401(k) retirement plan. The computers contained personal information about Petco’s current and former employees, including 1,320 in Massachusetts. Petco currently employs about 22,000 people nationwide.

The company said that the information on the computers was encrypted, so that it would be extremely difficult to decipher, and that there is no evidence criminals have used the data.

Massachusetts law requires companies doing business in the state to report such thefts, however.

Petco said that it will provide current and former Massachusetts employees with one year of credit monitoring service at no charge. Such services can help prevent criminals from using stolen identities to set up phony credit accounts or make unauthorized purchases.