China's Ministry of Transportation (MoT) said as many as 14 vessels are at the site of the collision in the East China Sea, including firefighting and search-and-rescue ships, with one more en route.
Cleanup boats are also on hand to deal with light crude spilled in the accident, though the extent of the spill is unclear.
Ministry of Foreign Affairs spokesman Lu Kang said that Chinese authorities were "positively cleaning the waste at the same time" as conducting search and rescue operations.
He added that the investigation into the collision and subsequent fire was "still going on," and that authorities would continue to provide updates.
The Panama-flagged SANCHI was carrying 136,000 tons -- around 42 million US gallons, or a million barrels -- of oil from Iran to South Korea when it collided with the Hong Kong-registered freighter, the CF Crystal.
The collision took place approximately 160 nautical miles (184 statute miles) east of the mouth of the Yangtze River, at about 8 p.m. local time (7 a.m. ET) Saturday, the Ministry of Transport said in a statement.
Thirty Iranians and two Bangladeshi citizens were reported missing from the tanker. One body, yet to be identified, has been found by search-and-rescue teams.
Chinese authorities warned on Monday that the tanker was at risk of exploding.
China's Ministry of Transport said Tuesday the tanker "is still on fire, and the rescue and fire monitoring work of SANCHI are still going on." Civilian fishing and "business" vessels were also involved in the search for missing crew members, the statement added.
Images from state broadcaster CCTV showed flames, and smoke billowing from the vessel.
The Hong Kong-registered CF-Crystal had been transporting food from the United States to the Chinese province of Guangdong, according to the MoT. The 21 crew members from the cargo ship were all rescued, it said.
It is not clear from the Chinese statement if South Korean vessels, which had assisted the efforts since the fires erupted on Saturday evening, were still actively involved in efforts to extinguish the blaze and search for the missing seamen.
With a length of 900 feet (274 meters) and displacing more than 85,000 tons, the SANCHI is almost as big as the US Navy's Nimitz-class aircraft carriers, according to the ship-tracking site marinetraffic.com
Iran's Shana news agency, which focuses on the country's petroleum and energy sectors, reported that the SANCHI was managed by the National Iranian Tanker Company and that its cargo was worth around $60 million. Shana said the oil had been purchased by South Korean customers.