Four people were missing Monday after a collision between two boats on the Red River.
The accident happened at around 11 a.m. off Hanoi, when it was foggy and raining heavily.
A boat controlled by Le Van Duong and carrying seven other people collided into another that was carrying sand from the northern province of Phu Tho to Hanoi.
Duong's boat sank, leaving four people on board missing.
Hanoi police are searching for the victims and trying to salvage the boat.