A passenger told local television channel TVB the scene on the bus was “very chaotic, we were crushed together”.
The coach seemed to have collided repeatedly with the kerb before coming to a stop, another passenger told the channel.
“The bus hit once, then hit left and right, and hit the roadside to stop,” the passenger said.
Television footage showed the kerb on either side of the road was damaged.
The accident happened at 5:00 am (2100 GMT Thursday).
In 2003 a double-decker bus collided with a truck and plummeted off a bridge, killing 21 people and injuring 20.
A speeding double-decker overturned in northern Hong Kong in February, killing 19 people and leaving more than 60 injured. The bus driver was arrested for dangerous driving.
That was the second deadliest bus accident in recent years in the semi-autonomous southern Chinese city, which prides itself on having one of the world’s best public transport systems.