(Updating to add Transport Ministry comment in 4th paragraph.)
BEIJING, Jan 17 (Reuters) - An Iranian oil tanker that sank in the East China Sea has left two oil slicks covering a combined 109 square km (42 square miles), the Chinese government said late on Tuesday, as maritime police scour for damage and prepare to explore the wreck.
Satellite imaging showed a slick of 69 square km (26.6 square miles) and a second 40 square km (15.4 square miles) 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 bodies of two sailors were recovered from the ship while a third body was pulled from the sea near the vessel. The remaining 29 crew of the ship are presumed dead.
In a statement on Wednesday, the Ministry of Transport said the salvage team had located the wreck, which was at a depth of 115 meters (377 feet) under sea level, and were preparing to send underwater robots to explore it.
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.
Clean-up teams continue to monitor the wreck area to assess the distribution and drift of the oil spill and the ecological impact.
The Sanchi 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.
The ship, which was carrying 136,000 tonnes or almost 1 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 does not see much chance that the spill will reach its shores.
(Reporting by Josephine Mason; Editing by Richard Pullin and Christian Schmollinger)