(Reuters) -- Satellite imaging showed a slick of 69 square kms (26.6 square miles) and a second 40 square km (15.4 square mile) slick, which is less thick and not as concentrated, the State Oceanic Administration (SOA) said in a statement.

The large tanker Sanchi (IMO:9356608) sank in the worst oil ship disaster in decades on Sunday, raising worries about damage to the marine ecosystem.

The vessel's crew of 30 Iranians and two Bangladeshis are all believed to have perished in the incident.

The SOA said vessels have taken 31 water samples in the area around the wreck containing black grease with heavy oil smells, and a concentration of petroleum that exceeds some seawater quality standard limits.

The news comes as clean-up teams continue to monitor the wreck area to assess the distribution and drift of the oil spill and the ecological impact.

The tanker had been adrift and ablaze after crashing into the freighter CF Crystal (IMO:9497050) on Jan. 6. Strong winds pushed it away from the Chinese coast, where the incident happened, and into Japan's exclusive economic zone (EEZ).

The ship, which was carrying 136,000 tonnes or almost a million barrels of condensate - an ultra-light, highly flammable crude oil - sank after several explosions weakened the hull.

On Tuesday, Japan's environment ministry said it doesn't see much chance that the spill will reach its shores.

(Photo: Transport Ministry of China, via European Pressphoto Agency)