PROVIDENCE, R.I. (AP) -- Officials were trying to determine what caused a blast Saturday morning that knocked a Rhode Island beachgoer to the ground, but left behind no obvious evidence of an explosive device.

Area of an explosion at Salty Brine Beach in Narragansett, Rhode Island (WCVB TV)

Salty Brine beach in Narragansett was evacuated after witnesses reported a possible explosion that knocked a woman into a rock wall.

State Department of Environmental Management spokeswoman Rayne Maguire tells the Providence Journal the woman was taken to a hospital. No other injuries were reported.

A witness reported hearing the loud noise 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 no evidence of a device that caused the loud boom.

"I can tell you there was definitely a ground disturbance there," he said.

Mouradjian says 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, and samples were being tested.

He said the beach would remain closed while the investigation continues.

"They are on their hands and knee sifting through the sand for any debris or evidence," he said.

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