The two people found dead within 1 km of each other at Kovan are suspected to have been murdered.
The man found dead inside a house in Hillside Drive was in his 60s, while the man found dead outside Kovan MRT station along Upper Serangoon Road was believed to in his 40s.
They are believed to be father and son.
A blood trail could be seen between the two locations.
An eyewitness said she saw a man being dragged by a car while she was driving along Upper Serangoon Road. About 20 cars were honking loudly at the driver but he or she did not stop, said the eyewitness
Officers from the Criminal Investigation Department (CID) were at Hillside Drive on Wednesday evening and have cordoned off a section of double-storey houses in the quiet residential estate.
Residents realised something was wrong when they spotted a blue police tent along Upper Serangoon Road near the MRT station.
Drivers also saw CID officers combing the road around The Girls' Brigade near Hillside Drive.