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MANCHESTER, Conn. (AP) _ An explosion at a pool supply company sent plumes of chlorine-filled smoke into the sky Thursday afternoon, and authorities asked about 100 residents to evacuate.

No serious injuries were reported and most of those evacuated were allowed to return to their homes late Thursday night.

The fire and chlorine release were under control by 9 p.m., Assistant Fire Chief Robert Bycholski said. Residents may be allowed to return late Thursday night.

The Journal Inquirer of Manchester said water somehow mixed with chlorine-based chemicals to cause the blast.

Department of Environmental Protection officials said their major concern was the toxic chlorine gas. Tests hours after the blast showed little chlorine in the air.

At least five people were hospitalized because of breathing problems, said Andrew Beck, a spokesman for the Eastern Connecticut Health Network. Some people reported smelling chlorine 20 miles away.