PHILADELPHIA (AP) _ A refinery storage tank exploded and caught fire this morning, injuring one person, officials said.

Firefighters sounded five alarms and police began rerouting traffic around the site in south Philadelphia after the 9:15 a.m. blast at Atlantic Refining & Marketing Corp.

Fire Department spokesman Capt. Angelo Saggiomo said firefighters contained the blaze to one tank at the refinery, about 50 yards from the frozen Schuylkill River.

Rod McIntyre, an Atlantic employee, said the tank, known as a ''sour water tank,'' held water on the bottom, hydrogen and sulfide in the center and some oil on top.

Officials were investigating whether the material in the tank was toxic.

The blast blew off the top of the tank, which is 40 feet high and 30 feet in diamter. It landed about 50 yards away, witnesses said.

McIntyre said one supervisor was injured by flying glass and treated at the plant infirmary.