A thunderstorm broke the roof of the Festival Walk mall in Hong Kong on Sunday night, allowing heavy rainfall to enter the mall, said the mall's owner on Monday.

Mapletree Greater China Commercial Trust Management, the manager of Mapletree Greater China Commercial Trust, which owns Festival Walk, said its staff were on site to render assistance.

Mapletree Greater China Commercial Trust Management said the "exceptional rainfall" had caused flooding in parts of the mall.

Itsstaff are in the process of assessing the damage caused and making the necessary insurance claims, it added.

Mapletree Greater China Commercial Trust is listed on the Singapore Exchange. Apart from Festival Walk, the other property in its portfolio is office development Gateway Plaza.

Units of Mapletree Greater China Commercial Trust were down 1 cent to 81.5 cents by 11.40am on Monday.