Officials do not know what caused a blast that knocked a Rhode Island beachgoer to the ground but concluded there is no public threat and no reason to keep the beach closed.

State Department of Environmental Management Director Janet Coit said in a statement late Saturday that Salty Brine beach in Narragansett would reopen Sunday.

"The on-site investigation is now complete, and there is no reason to believe there are any public safety concerns related to today's incident," she said.

Col. Steven O'Donnell of the Rhode Island State Police said the investigation found no evidence that an explosive device caused the loud boom.

Officials did not offer a cause for the blast.

The beach was evacuated late Saturday morning after witnesses reported a possible explosion that knocked a woman into a rock wall.

DEM spokeswoman Rayne Maguire told the Providence Journal the woman was taken to a hospital. No other injuries were reported.

A witness reported hearing the loud noise and seeing the woman get knocked over a few feet from him.

"It was like an M-80 boom, like a grenade," Mario Lewis of West Greenwich told the newspaper.

DEM Associate Director Larry Mouradjian told the Journal there was "definitely a ground disturbance there."

Mouradjian said a report of a suspicious person was checked out but investigators' concerns were satisfied.

He said some people reported some sort of chemical smell, such as sulphur or butane.