The management board of the UNESCO World Heritage Site Phong Nha – Ke Bang National Park said the situation had worsened since a flood last October.

As of Thursday, tour boats had to stop outside the cave and tourists had to get inside on foot. Deposits had also mixed with many of the most beautiful sand beaches inside the cave, changing their colors.

“It’s never got this bad before,” said Hoang Van Ninh, owner of a tour boat. Ninh said the situation was getting worse after the Lunar New Year. The flows were blocked as far as one km outside the cave.

The October flood isn’t the root cause. Nguyen Van Huyen, Vice Director of the national park said the cause was the deformation of the Tra Ang Stream to which Phong Nha Cave is connected.

This stream is being reshaped and thus seriously polluted by construction activities of a museum project.

The project’s investor, 12 Corps, has authorized 185 Factory to carry out construction at the head of the stream. The latter, in turn, has contracted Tuan Cuong Ltd. to execute the project.

Tuan Cuong’s president, Truong Tuan Dung said his company couldn’t be held responsible because it didn’t sign a commitment to protect the environment as it was only a contractor. (The law requires all parties working inside the national park to sign such a commitment.)

Since construction started, local residents along the stream said native species such as leaf monkeys and pheasants had also left the area.

“Whatever they are doing there, mud is flowing here,” said Hoang Van Dai, Vice President of Phong Nha – Ke Bang Ecology and Cuture Tourism Center, which has spent hundreds of millions to clean up the river flows inside the cave.

Dai said he had informed the Quang Binh Province People’s Committee of the problem.

For his part, the national park’s director Luu Minh Thanh was surprised to know that Tuan Cuong Ltd. hadn’t signed the commitment. Thanh said he would immediately investigate the matter and ask 12 Corps to stop any harmful activity.