Green algae is continuing to spread across the Yellow Sea and East China Sea, local maritime officials said Wednesday.

The mass of green algae, namely enteromorpha prolifera, expanded from 130 square kilometers on Tuesday to 150 square kilometers on Wednesday, according to the North China Sea Branch (NCSB) of the State Oceanic Administration.

Rising water temperatures have supported the algae's quick growth, said Gao Song, a forecaster with the NCSB.

Gao estimated that the algae might reach the waters off the city of Qingdao, Shandong Province, in a week. The ocean's current as well as wind direction move the algae along, he said.

The NCSB first detected the algae off the city of Yancheng in Jiangsu Province on May 28. At that time it covered 6.8 square kilometers of sea.

Although the green algae is not poisonous, it can consume large amounts of oxygen which can threaten marine life. Also, rotten algae emits a foul smell which can hinder tourism along affected coastlines.

Green algae emerged in the Yellow Sea in 2007. Local residents and soldiers removed tens of thousands of tonnes of it in 2008 before the sailing events of the Olympics in Qingdao.