Two bodies were found in Kovan about a kilometre from each other.
A blood trail could be seen between a private house on Hillside Drive and outside Kovan MRT station on Upper Serangoon Road, where each of the bodies were believed to have been found.
Officers from the Criminal Investigation Department were on the scene on Wednesday evening, and a lane along Upper Serangoon Road was blocked off.
An eyewitness said that she saw a man being dragged by a car while she was driving. About 20 cars were honking loudly at the driver but he or she did not stop, said the eyewitness.