An Iranian oil tanker sailing to South Korea collided with a cargo ship off China’s coast and caught fire, leaving at least 32 people missing on Sunday.

The tanker Sanchi departed Iran’s Assaluyeh port on Dec. 16 for Daesan in South Korea carrying about 1 million barrels of natural gas condensate, according to ship-tracking data compiled by Bloomberg. State-run shipper National Iranian Tanker Co. owns the Panamanian-flagged vessel, according to ship data compiled by Bloomberg.

The Sanchi collided with the Chinese cargo vessel CF Crystal about 160 nautical miles off the coast of Shanghai on Saturday, according to Iran’s Oil Ministry news agency, Shana. The 32 crew members of the Iranian vessel were missing, it said. China’s Ministry of Transport also reported the collision Saturday and said the Sanchi was on fire and that search and rescue operations were under way. It said oil was on the water. Shana and the China agency didn’t report the cause of the crash.

Iran, the third-largest oil producer in the Organization of Petroleum Exporting Countries, sells most of its crude oil and condensate to Asia, exporting about 2 million barrels a day. Condensate is a light oil produced along with natural gas, mainly at Iran’s offshore South Pars fields. The port of Assaluyeh is the main loading point for Iranian condensate.