Media playback is unsupported on your device Media caption Hong Kong's chief executive has ordered an inquiry into the incident

A collision between two passenger boats off Hong Kong has left at least 36 people dead, officials say.

One of the boats was carrying more than 120 people to a fireworks display when it half-sank following Monday night's collision near Lamma Island.

Twenty-eight people were pronounced dead at the scene. About 100 others have been taken to hospital, eight of whom were later said to have died.

A large-scale air and sea search for survivors is still continuing.

A Hong Kong government statement said: "Over 100 people were sent to five hospitals during the incident; nine of them have sustained serious injuries or are in critical condition."

Analysis Unlike mainland China, transport accidents resulting in fatalities are extremely rare in Hong Kong. This city of more than seven million people prides itself on highly regulated, efficient forms of mass transport by road, underground and by sea. Hong Kong was founded as a deep-water port more than 150 years ago. Its surrounding waters are home to some of the busiest shipping routes in the world. Its location close to the Pearl River Delta means vessels carrying cargo ply those waters everyday. In addition to the commercial ships, leisure and fishing boats are common sights, but serious collisions are uncommon. Thousands of people take regularly scheduled ferries from Hong Kong's main islands to outlying territories such as Lamma Island, which is a very popular area for both tourists and residents.

Rescue work would continue, the statement added, because the fire department could not rule out that there were still people inside the vessel or missing.

The collision occurred during a busy period for passenger travel in Hong Kong, at the end of a long holiday weekend to mark the mid-autumn festival that this year coincides with China's National Day on 1 October.

Power company Hong Kong Electric has confirmed to the BBC that it owned the boat which sank. It was taking staff and family members to watch National Day fireworks in Victoria Harbour.

The vessel and another boat - reportedly operated by Hong Kong and Kowloon Ferry - collided, causing the HK Electric vessel to list, a company official was quoted as saying.

The other boat reportedly had about 100 people on board.

It was slightly damaged in the crash but returned safely to port, according to Radio Television Hong Kong. A number of passengers on board were treated for minor injuries.

'High speed'

Hong Kong Chief Executive CY Leung promised an investigation into the accident.

"All of Hong Kong's emergency forces are focused here," he said. "Wide-ranging rescue work is being carried out in the sea, on land and in the air."

Image caption Dozens of people were taken to hospital after the accident

Dozens of boats and two helicopters were involved in the search.

The crash happened about 20:30 local time (12:30 GMT) on Monday. Low visibility and the many obstacles on the vessel made it difficult for people to escape the listing ship, says the BBC's Juliana Liu in Hong Kong.

One survivor told The South China Morning Post: "After 10 minutes out, a boat crashed into ours from the side at very high speed. The rear... started to sink. I suddenly found myself deep under the sea.

"I swam hard and tried to grab a life buoy," added the man. "I don't know where my two kids are."

Witnesses said the boat went under very fast.

"Within 10 minutes, the ship had sunk. We had to wait at least 20 minutes before we were rescued," Reuters news agency quoted one man as saying.

"We thought we were going to die. Everyone was trapped inside," another woman said.

Sarah Blackman was on the ferry involved in the collision.

"I was on the top deck of the ferry and felt the impact - it threw people off of their seats," she told the BBC. "The sound the collision made was horrific."

"As my ferry docked in Lamma, it was clear everyone was in shock and desperately concerned for the ship left behind."

Lamma lies some 3km (two miles) south-west of Hong Kong island, and is popular with tourists and expatriates.

Hong Kong is one of the world's busiest shipping channels, but its ferries have a good safety record.