HANGZHOU - Seven people were rescued, but four remained missing, after two boats slammed into each other early Sunday morning off the coast of Zhejiang, local border defense department said.

The accident happened near Dachen Island around 2:40 am near the city of Taizhou. Both boats were registered in Zhejiang province, according to the border defense department of Taizhou.

One boat sank with 11 crew members aboard. Rescuers lifted seven from the water, and were still searching the other four, the statement said.

The cause of the accident is being investigated.