Six crew from two passenger boats that collided killing 37 people in Hong Kong's worst maritime accident in decades have been arrested, the territory's security chief said Tuesday.

"Police arrested six individuals this afternoon... They are being investigated for endangering people's lives at sea," Security Minister Lai Tung-kwok told a press conference a day after the collision.

He said three crew members of the company pleasure craft that sank in the incident, and where all the fatalities occurred, were detained along with three from the regular ferry vessel that collided with it near Lamma island.

Police chief Tsang Wai-hung said the suspects were responsible for the boats' operation.

"We don't rule out more arrests," he added.

Hong Kong chief Leung Chun-ying told the same press conference that the toll from the collision had risen by one to 37, with more than 100 injured.

More than 120 passengers and crew were on the Hong Kong Electric company's vessel to watch the huge National Day fireworks display in Victoria Harbour on Monday evening when it collided with the ferry.

Scores of people were thrown into the choppy water and the company vessel sank within minutes, leaving only its bow protruding from the waves.

The ferry limped the short distance to Lamma and disembarked its passengers as it was taking on water.