At least 19 punters were killed when a bus returning racegoers from Sha Tin to the city crashed on Saturday afternoon.
A total of 19 people, 17 men and two women, have been confirmed as dead with a further 40 people being treated for injuries.
The double-decker bus was returning to Hong city central when it turned over on a bend on Tai Po Road - the second longest road in Hong Kong
One passenger told the South China Morning Post the bus felt it was going faster than usual.
"It was much faster than I normally felt in a bus," the passenger said. "And then it was like the tyre slipped and the bus turned. It was really chaotic in the bus.
“People fell on one another and got tossed from side to side.”
Police arrested the driver for dangerous driving causing death and dangerous driving causing grievous bodily harm. He was injured but it was unclear whether he needed hospital treatment, a police spokesman said.
The Hong Kong Jockey Club issued a statement on Saturday evening.
"The Hong Kong Jockey Club is most saddened to learn that a public bus transporting passengers following today's race meeting was involved in an accident with numerous casualties reported,” the statement read.
"The Club would like to express its deepest condolences to the families of the victims and sympathies to those injured.
“The Club is closely monitoring the situation and considering how it can help."