Residents of Yishun Street 81 spotted a 5kg potted plant lodged in the windscreen of a Toyota sedan that was parked in the Housing Board estate on Sunday.
The police said yesterday that they received a call about the incident at Block 871 on Sunday at 2.23pm.
The case has been classified as a rash act and investigations are ongoing.
The potted plant apparently fell from the ninth floor of the HDB block.
It crashed through the windscreen of the Toyota parked under the block.
It was not clear if the potted plant, which damaged the car's dashboard and gear box, had fallen or was thrown by someone. The plant belongs to a 78-year-old retiree who lives on the ninth floor of the block, reported Chinese evening newspaper Shin Min Daily News.
Residents told Shin Min that police officers who responded to the case on Sunday had reviewed CCTV footage from cameras in the lifts.
They also said there was a similar incident at the block just two months ago.
Last month, an elderly woman landed in hospital after she was hit by a bicycle tyre thrown from a block of flats in Eunos Crescent.
A 16-year-old boy was later charged in court in connection with the incident, the latest in a recent series of "killer litter" cases in the neighbourhood.