Only 14 survivors, one of them the captain, have been found after the ship carrying 456 overturned in a freak tornado on Monday night.
Rescuers are searching the cabin of the ship, which was righted on Friday, looking for more bodies, the official People's Daily, wrote on its microblog.
Jiang Zhao, general manager of the company which operated the Eastern Star, bowed in apology for the disaster during an interview with state media reported late on Friday, saying they would "fully" cooperate with the investigation.
Beijing has pledged there would be "no cover-up" in the probe.
Police have detained the captain and chief engineer for questioning. An initial investigation found the ship was not overloaded and had enough life vests on board.
More than 1,000 family members have come to Jianli in the central province of Hubei, where the ship went down, with many expressing frustration at a lack of information from the government.
On Friday, an irate relative of two passengers missing aboard the ship burst into a just-concluded news conference with senior officials and publicly accused the government of treating its people like enemies.