SHANGHAI — The Chinese and South Korean authorities on Sunday were searching for 32 crew members who went missing after their oil tanker collided with another ship off China’s east coast the night before.

The site of the collision, which happened roughly 160 miles off the coast of Shanghai at 8 p.m. Saturday, according to China’s Ministry of Transportation, is in the middle of seas with heavy shipping traffic between China and South Korea.

The oil tanker, registered in Panama, collided with a bulk freighter registered in Hong Kong. The government said that all 21 crew members of the bulk freighter had been rescued, while the 32 missing were from the oil tanker.

Of those missing, 30 are Iranian citizens and two are from Bangladesh, according to the Chinese government. The 21 rescued are all Chinese citizens.