A motorist who allegedly drove off after running over a woman in Cantonment Road was arrested last Friday, five days after the accident.
The 44-year-old driver had left the scene before the police arrived and was arrested for failing to render assistance, the police said.
She is the second person held in relation to the Jan 5 accident, in which Madam Ong Soh Boey, 69, died.
The Straits Times understands the woman was driving a Honda Freed at the time of the accident.
A 25-year-old Maserati driver, whose car was on the wrong side of the road, was arrested on the same day of the accident for dangerous driving causing death.
A video clip of the accident soon circulated online showing that a second, yellow car was also involved. Madam Ong, who was lying on the road, was hit again and dragged several metres by the yellow car.
Madam Ong, who was riding an electric bicycle, was pronounced dead at the scene by a paramedic.
The single mother of two daughters, was riding near Pinnacle@ Duxton when the accident occurred. Her family told ST that she was then on her way to a provision shop that she ran in Chinatown.
Despite being financially stable, she had taken on several part-time jobs, including cleaning and washing laundry, to fill her time.
Her family said Madam Ong, who reportedly split with her husband nearly 40 years ago, had been riding a bicycle between home and work almost every day for 30 years without incident.
"My aunt was a strong and independent woman. She was also kind and thrifty, but generous to others," said Madam Ong's niece, who declined to be named.