MANILA - Fast fashion retailer Forever 21 said Tuesday it was investigating possible "unauthorized access" to data from credit cards, as it advised shoppers to monitor their payment card statements.

The Los Angeles-based company, which operates 600 stores worldwide, including the Philippines, did not comment on the extent of the potential breach.

The investigation is focused on card transactions in Forever 21 stores from March to October this year, the company said in a statement.

"Because the investigation is continuing, complete findings are not available, and it is too early to provide further details on the investigation," the statement said.

"We regret that this incident occurred and apologize for any inconvenience. We will continue to work to address this matter. For more information," it said.

Customers should "closely monitor" their payment card statements, Forever 21 said.

"If customers see an unauthorized charge, they should immediately notify the bank that issued the card," it said.