Authorities in Hong Kong have announced a three-day mourning period in the city to mourning the deaths of victims of a ferry collision, which is Hong Kong's worst maritime accident in four decades.

Flags around the city flew at half mast on Thursday, when Chief executive Leung Chun-ying will hold a three minutes of silence at the government headquarters. Schools and other public institutions are also expected to fall silent at noon.

A high-speed ferry named, Sea Smooth collided with a pleasure craft, the Lamma IV that was carrying about 120 passengers to a spot to witness the national day fireworks on Monday evening. The left rear of Lamma IV was torn apart and several passengers were thrown into the sea and water filled in within minutes and trapped passengers in the underwater cabins.

The authorities have announced a six month investigations into several questions including whether there was adequate safety equipment on board and if the captains of the vessels followed the rules of the sea. The investigations will also find out the reason for the sinking of the vessel so quickly.

The British Prime Minister David Cameron, US Consul General Stephen Young and several others have sent their condolences to the victims.