Efforts to remove the remaining cargo of a stuck oil tanker just off the China coast are underway.

The vessel's manager said Friday it was siphoning the oil inside the tanker, which ran into trouble after a collision caused by bad weather.

Goodwood Ship Management, the owner of the Liberia-flagged tanker called the "A Symphony," said it had received clearance from China's Maritime Safety Administration to begin rescue and recovery operations.

China maritime officials said earlier the ship had spilled hundreds of tons of oil into the sea. On Friday, officials revised down their initial numbers from 500 tons to 400 tons. Officials said the spill had since been contained.

Officials at the Shandong Maritime Safety Administration said the spill has since been contained. The agency said the cargo of the vessel, which is around 150,000 tons of bitumen blend, remained unchanged. Officials said this indicated that the ship was no longer leaking oil.

Goodwood Ship Management said the A Symphony was anchored when it was hit by the bulk carrier Sea Justice Wednesday. The collision occurred during a dense fog. The company said the impact had caused a small breach on one of the ship's cargoes and ballast tanks.

Qingdao Glory Ships Co, the owner of the bulk carrier, has yet to issue a statement in response to the incident.

The Shandong Maritime Safety Administration said the accident happened just 40 nautical miles southeast of the Qingdao Port. The agency said ship traffic to and from the port remained unaffected by the incident.

Residents living in nearby coastlines have not yet reported any obvious signs of a spill. However, some residents have expressed concerns about possible contamination to their food supply.  

Bitumen mix, a type of heavy crude oil and residue, is mainly used for road surfacing and roofing. It is also used by China's independent refiners as an alternative to refining feedstocks as it is much cheaper to import than crude oil. The substance is toxic and exposure can cause issues such as bronchitis, emphysema, lung cancer and stomach cancer.