Police and firefighters in Narragansett, Rhode Island, were investigating an apparent explosion at a beach that injured one woman.

Salty Brine Beach was being evacuated while a bomb squad investigated, according to the Rhode Island Department of Environmental Management.

Rayna Maguire, a department spokesperson, said a preliminary investigation reveals the explosion came from underneath the sand. A 50-year-old woman had been taken to South County Hospital after witnesses say she was thrown onto the rocks of the jetty by the explosion, according to CBS affiliate WPRI. Details on victim’s injuries were unclear.

DEM enforcement Sgt. Thomas Silvia told the Providence Journal that authorities are looking for a suspect they believe planted something in the sand, and then fled toward Rogers Williams state beach.

Mario Lewis of West Greenwich told the paper he heard the boom that knocked over the woman about three feet from him, but saw no debris or smoke.