The spread of green algae floating towards east China' s coastline is continuing and has reached the sea off Jiangsu Province, an oceanic official said Wednesday.

The green algae, floating southward from the sea of the neighboring Shandong Province since Monday, has covered tens of kilometers as far away as in the waters off Lianyungang City of Jiangsu Province, said Zhu Kongwen, deputy chief of the city' s oceanic and fishery department.

The city has begun an emergency response and cleaning vessels have been organized to control the spreading algae.

In Shandong, the expanse of the green mass reached 320 sq km Tuesday, 120 sq km more than the coverage reported Monday, according to data released by the North China Sea Branch of the State Oceanic Administration Wednesday.

Modern societies often see polluted runoffs into waterways, particularly made up of chemicals such as nitride and phosphide, causing the growth of excessive nutrients in the ocean, known as eutrophication, which is the main reason for the fast-paced spread of the green algae, said Wu Jianxin, associate professor of marine science from Huaihai Institute of Technology.

The large expanse of green algae could block the sunshine and dead algae would then consume large amounts of oxygen, adversely affecting the growth of marine organisms, Wu said.