SINGAPORE - A drone spotted flying around a Punggol Housing Board estate is the subject of an investigation by the Civil Aviation Authority of Singapore (CAAS).

The authority told The Straits Times on Wednesday (Sept 26) that it has not issued any activity permit for unmanned aircraft operations at the Treelodge@Punggol estate this month. CAAS added that it is investigating the matter.

A permit is required to operate unmanned aircraft, otherwise known as drones, in the area, as the estate is located within 5km of Paya Lebar Air Base.

A video of the drone was uploaded online by Facebook user Alex Lee last Friday. It shows the drone flying close to two buildings around the estate.

The drone is seen pausing for short moments outside some windows, while Mr Lee's wife and sister can be heard discussing if the drone was peeking into residents' rooms and toilets.

The video has garnered more than 263,000 views and almost 5,000 shares since it was uploaded.

Mr Lee, a 34-year-old claims manager, told ST that the video was filmed from the 10th floor of the estate on Sept 12. The drone was hovering at a similar height.

His wife was visiting his sister, who lives there, and it was the first time the two have seen a drone flying in the area, Mr Lee said.

Since the incident, his sister's family have made it point to draw the curtains in their home.

Mr Sidney Koh, director of air navigation services policy at CAAS, said unmanned aircraft operators are required to obtain activity permits to fly such devices in areas within 5km of where aircraft flight operations take place.

Before flying their drones in these areas, operators are also advised to seek permission from the relevant building or land manager, and are encouraged to inform residents and tenants.

Owners and managements of private properties should report sightings of illegal drone operations to the Singapore Police Force.

"Members of the public are also advised to contact the police should they encounter an unmanned aircraft being flown in a manner that may be an intrusion of privacy or cause harassment," said Mr Koh.