More than 10 vessels from South China's Guangdong Province are joining efforts to rescue 11 missing crew after two ships collided near the waters of Hong Kong's Po Toi Island on Monday morning, local authorities said.

A Chinese mainland cargo ship sank after colliding with another cargo vessel at around 2:30 am local time. Twelve crewmen fell into the sea and one of them, a 47-year-old man from the mainland, was later rescued by a passing fishing boat, according to the Hong Kong Maritime Department.

The Guangdong Provincial Maritime Search and Rescue Center launched an emergency response and sent three patrol and rescue ships as well a helicopter to assist with the rescue.

Another 12 vessels and two rescue helicopters are also joining the mission, according to theMinistry of Transport.

The Chinese ship, Zhong Xing 2, was carrying cement when it collided with the 300-meter Marshall Islands-registered container ship, MOL Motivator, which was leaving Hong Kong for Guangdong.

MOL Motivator, which has a dry weight tonnage of 79,400 tones according to Thomson Reuters data, was travelling from Hong Kong to Yantian port in southern China.

Vessels navigating near the collision site have been warned there may be a sunken ship nearby and have been asked to stay away.

The Hong Kong Observatory issued an amber rain warning, signaling expectations of heavy rain in parts of the territory overnight.

The Hong Kong Maritime Rescue Coordination Center is assisting with the search and rescue operation coordinated by the Guangdong Maritime Rescue Coordination Center. Five Marine Police launches three fireboats and a Government Flying Service helicopter from Hong Kong are involved in the operation.