The main entrance to the Hilton Singapore has been completely boarded up after the ceiling of the hotel's driveway collapsed on Sunday afternoon.

The ceiling - made of plasterboard with an aluminium frame - fell on two vehicles, and four people were taken to hospital.

Visitors now have to make their way to the lobby via the entrance to the hotel's shopping gallery, located about 15m away from the main entrance.

The hotel's taxi stand has also been shifted to this entrance.

Experts have speculated that the recent heavy rain could have caused water to seep through to the false ceiling, causing it to collapse.

"All our efforts are currently focused on fully cooperating with the local authorities on their current investigation so that we can rectify the affected area as soon as possible," said a spokesman for Hilton Singapore, adding that the people who were injured have since been discharged from the hospital.

Investigations into the cause of the incident are ongoing.