Pfizer Inc. has agreed to pay a $22,500 penalty for failing to properly notify state and federal officials about a chemical release at a Connecticut research and development plant.

The U.S. Environmental Protection Agency said Tuesday that an explosion in June 2002 at Pfizer’s Groton plant released about 1,400 pounds of tetrahydrofuran, a solvent used in pharmaceutical manufacturing. Seven people were injured.

Tetrahydrofuran is highly flammable and may contribute to the release of toxic gases and vapors during a fire, according to the federal Occupational Safety and Health Administration.

Pfizer failed to immediately notify the National Response Center of the release, the EPA said, in violation of federal law. It also failed to immediately notify the state Emergency Response Commission, the EPA said.

Pfizer spokesman Stephen Lederer said the company regrets the late reporting, but its priority was “naturally to protect the safety of our colleagues and neighbors.”

New York-based Pfizer has its research and development headquarters in Groton and New London.