A floating expanse of green algae floating off China's eastern seaboard is growing and spreading further along the coast, state-run media has reported.
The algae bloom has expanded by about 50 percent since it was first reported by state media earlier in the week to 320 square kilometres (120 square miles), or about four times the size of Hong Kong island, Xinhua news agency said.
The algae island was previously situated several kilometres off the coast of Shandong province but has expanded southwards to waters off neighbouring Jiangsu, it said in a dispatch late Wednesday.
Algae blooms are typically caused by pollution in China and suck up huge amounts of oxygen needed by marine wildlife to survive and leave a foul stench when they wash up on beaches.
The report, which quoted the State Oceanic Administration, gave no indication how close the algae bloom was to the coast or whether it was moving towards the shore.
Earlier in the week Xinhua said it was drifting toward Shandong, spurring the local branch of the State Oceanic Administration, which monitors marine conditions, to dispatch vessels in a bid to clear the algae.
It had warned that the bloom could threaten marine life and the region's tourism industry.
In August 2008, a large offshore algae bloom threatened the sailing competition of the Olympic Games when it engulfed waters surrounding the event's venue in the eastern Chinese city of Qingdao, near Jiaonan.
Up to 10,000 soldiers and volunteers were enlisted to clean up more than a million tonnes of the foul-smelling algae as they raced to clear the waters in time for the Olympics.
According to a 2008 State Oceanic Administration report, raw sewage and pollution from agricultural run-off has polluted 83 percent of China's coastal waters, leading to algae and other problems.
Explore further: Spain defends Canaries oil drilling plan