A bus and a storefront are heavily damaged after the vehicle rolled downhill on Monday in Macao. [Photo/Xinhua]

Officials from the fire department that conducted the rescue said three of the injured were in serious condition. All were taken to a hospital.

The handbrake is thought to have failed after the bus stopped on a slope, the Macao Public Security Police Force said, and the vehicle rolled downhill, crashing into a clinic next to the road.

The driver was not in the bus.

The injured passengers were from a tourist group organized in Shenzhen, Guangdong province, who had arrived in Macao at about 9 am on Monday and planned to leave in the afternoon.

The driver, a resident of Macao, has seven to eight years of experience in driving and passed a sobriety test, media in Macao reported.

The accident is being investigated.

Chinese mainland tourists made 20.4 million trips to Macao last year, accounting for two-thirds of tourist visits to the special administrative region last year, according to the regional government.