A 19-year-old woman died and her 24-year-old boyfriend was injured after they were hit by a shuttle bus in Tuen Mun on Thursday morning.
Police arrested the 69-year-old bus driver on suspicion of dangerous driving causing death.
On Thursday afternoon, the man was still being held for questioning in Tai Po police station and no charge had been laid.
Police are appealing witnesses to contact officers on 3661 3800. Officers from the New Territories North traffic unit are investigating.
Fung Tin-yu, 19, was being accompanied to home by her boyfriend on the eve of Valentine’s Day when the accident happened shortly before 6.30am.
According to police, the two lovers were knocked down by the shuttle bus while crossing Pui To Road near the junction with Tuen Mun Heung Sze Wui Road.
Suffering serious head injuries, Fung was taken unconscious to Tuen Mun Hospital, where she was declared dead at 6.48am.
Her boyfriend was now being treated for head and leg injuries in the same hospital. After leanring his girlfriend's death, the man became emotional and was unfit to give a statement to police.
The shuttle bus serving a luxury housing estate in Tuen Mun was taken to a government vehicle plant for examination.
A police investigator said they were looking at the accident from all angles to establish its cause.
It is understood officers are investigating whether the two lovers were jaywalking at the time of the incident and whether the shuttle bus driver followed traffic lights to make a right turn into Pui To Road from Tuen Mun Heung Sze Wui Road.
Police figures show 115 people were killed in 113 fatal traffic accidents last year. In 2012, 120 people were killed in 116 accidents.