Huo Chuanlin, an official from China's State Oceanic Administration, holds a photo showing a rescue ship and an oil slick during a press conference on the Iranian oil tanker Sanchi, which exploded and sank after a collision in the East China Sea in January, at the Information Office of the Ministry of Transport in Beijing on Thursday. Photo: AP

Chinese authorities have coordinated efforts to continue clean-up operations in the East China Sea where an Iranian tanker sank more than two weeks ago, officials said Thursday.

As of Tuesday, five Chinese vessels, a Japanese vessel and a South Korean ship have cleaned a total of 225.8 square nautical miles, said Zhi Guanglu, an official with the Ministry of Transportation, at a press conference in Beijing.

"We are also making plans to clean residual oil underwater with the help of underwater robots to root out the hidden risks from the oil spill," Zhi said, noting that the ship also carried 1,900 tons of fuel oil.

China's marine, environmental and agricultural authorities have been closely monitoring the situation since the accident.

Besides sending ships and planes, satellite remote sensing has been used to monitor up to 800,000 square kilometers of sea surface.

As of January 28, the detected oil slick zone had shrunk to 30 square kilometers from 328 square kilometers on January 21, according to Huo Chuanlin, an official at the State Oceanic Administration, citing official satellite remote sensing data.

Agricultural departments have also assessed nearly 500 samples from 40 locations. Fishing vessels are now allowed to enter areas within a radius of 30 nautical miles around the sinking site.

"Based on the latest monitoring results, the oil spill remains a stable and controllable influencing factor for fishing resources as of now," said Han Xu, an official at the Ministry of Agriculture.

The Panama-registered, Iranian-owned oil tanker Sanchi, carrying 113,000 tons of light crude oil, collided with the CF Crystal, a Hong Kong-registered bulk freighter, about 300 kilometers east of the Yangtze estuary on January 6 and sank on January 14.

The 32 crew members onboard the tanker - 30 Iranians and two Bangladeshis - were lost.