"We have closed the park effective immediately, for public safety reasons, now that experts have assessed the situation. Wailua River tour boats will not be allowed to land," said Peter Young, DLNR chairperson, said in a news release. "Recently, several rocks have fallen, striking the viewing area. One was a boulder 4-feet across."

He added: "Fern Grotto experienced rockfalls during the height of the heavy rains in February and March. Sections of walkway were subsequently closed off."

An area above the Fern Grotto was inspected today by specialists, who determined there are a number of rocks that appear to pose an immediate danger to anyone standing below the grotto entrance, where visitors to this popular attraction congregate to take in the view, the news release said.