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A burning Iranian tanker listing for days off the coast of China after a collision with another vessel sank Sunday, with an Iranian official saying there was "no hope" of survival for the 29 missing sailors onboard.

Iranian state television reported that the Sanchi had sunk Sunday, days after its collision in the East China Sea. An anchorwoman on state television also offered condolences on behalf of the nation for the loss.

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China's state broadcaster confirmed the ship had sunk and also said the ship's voice data recorder, which functions like "black boxes" on aircraft, had been recovered.

The cause of the collision, 160 miles off the coast of Shanghai, remains unclear. Three bodies have been recovered from the sea, leaving 29 crew members still unaccounted for. The crew was all Iranian expect for two Bangladeshis.

Iranian state TV had earlier quoted the chief of Iran's maritime agency, Mahmoud Rastad, as saying: "There is no hope of finding survivors among the (missing) 29 members of the crew."

The Chinese freighter CF Crystal, which collided with the Panamanian-registered tanker, had 21 crew members, all of whom were reported safe.

Smoke and flames rise from the burning Iranian oil tanker "Sanchi" at sea off the coast of eastern China on Jan. 14, 2018. Transport Ministry of China / AFP - Getty Images

Thirteen ships, including one from South Korea and two from Japan, were engaged in the rescue and cleanup effort Saturday, spraying foam in an effort to extinguish the fire. The tanker was carrying a cargo of nearly 1 million barrels of condensate, a type of gassy, ultra-light oil that readily evaporates or burns off in a fire, reducing the chance of a major oil spill.

Intense flames, bad weather and poor visibility have all hampered rescue efforts.