The U.S. Securities and Exchange Commission has asked Pfizer Inc. for information about two of its painkillers, Celebrex and Bextra, the Associated Press reported Tuesday.

The company wouldn’t elaborate, except to say it is cooperating with the request, which was made in the second quarter of this year, the wire service said. Both drugs belong to a class of painkillers called cox-2 inhibitors, which also includes the Merck and Co. drug Vioxx.

Bextra and Vioxx have been withdrawn from U.S. markets after research linked them to higher rates of heart attack and stroke in long-term users.

Merck withdrew Vioxx September 30, 2004 and Pfizer pulled Bextra from pharmacy shelves in April, 2005.

Celebrex remains on the market but includes new warnings required by the U.S. Food and Drug Administration about possible cardiovascular risks.