Chinese officials say the cleanup of last week's oil spill at the mouth of the Pearl River is going smoothly. But, oil is still leaking from the container ship involved in the collision, and authorities remain concerned about the threat to nearby waters.

Over a thousand tons of oil has spilled since a Panamanian and a German flagged container ship collided on Tuesday near the mouth of the Pearl River in Guangdong Province.

Authorities say they have about a hundred boats working on decontamination in the area, and cleaning oil from the water. To date, a number of large slicks have been contained.

But divers haven't been able to plug the leak in the German-flagged ship, the MSC Ilona. Xu Guoyi, deputy director of Ministry of Communications' Maritime Bureau says “Our biggest task now is to deal with the leaking ship. It’s very difficult for us. Our divers can’t get to the crash site because of the strong winds and heavy waves. And we can’t tow the ship to shore because there’s a white dolphin preservation zone nearby, and we can't head north into Hong Kong waters.”

However, experts have designated a safe zone for the vessel, and decontamination ships are following it to monitor and clean up leaking oil as it heads there. China has reported the incident to the International Maritime Organization.