SAN FRANCISCO – Hackers broke into one of AT&T Inc.’s computer networks and stole credit card data and other personal information from several thousand customers who shopped at the telecommunication giant’s online store.

AT&T said it was notifying “fewer than 19,000” customers whose data was accessed during the weekend break-in, which it said was detected within hours.

The company said it immediately shut down the online store, notified credit card companies, and was working with law enforcement agencies to track down the hackers.

“We recognize that there is an active market for illegally obtained personal information,” Priscilla Hill-Ardoin, AT&T’s chief privacy officer, said in a statement.

“We will work closely with law enforcement to bring these data thieves to account,” Hill-Ardoin said.

AT&T said it would also pay for credit monitoring services to assist in protecting the customers involved. The data theft involved people who had bought DSL equipment for high-speed Internet access.