BORACAY ISLAND -- Five of 9 wetlands here have yet to be cleared of informal settlers and illegal structures, an environment official said, as the tourism industry prepared to reopen on Friday.

Four wetlands have been cleared and will be developed into sustainable public spaces with the help of Energy Development Corp, LT Group, San Miguel Corp and the Aboitiz Group, Environment Undersecretary Benny Antiporda told ABS-CBN News.

The wetlands serve as the "kidneys" of the island, filtering inland waste water before it flows to the sea, he said.

President Rodrigo Duterte closed the islands to tourists in April, saying pollution had turned some waters into "cesspools."

Informal settlers remain in one wetland near the port, Antiporda said, adding the government was looking for a relocation site.

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Some 32 families from the Tumandok tribe still occupy another wetland, but they will be relocated once land reform program in the island is finalized, he said.

Three hotels built on separate wetlands have yet to be demolished due to pending court cases, Antiporda said.

The management of the wetlands cannot be entrusted to communities as some residents are responsible for illegal structures built on the bodies of water, Antiporda said.