A massive power outage, triggered by malfunctioned electrical substations, affected 100,000 households in Macao on Wednesday, officials said.

The power outage, which occurred at 10:55 a.m. local time (0255 GMT), lasted about 1 hour and 30 minutes and affected central and northern Macao peninsula including Zona Nova de Aterros do Porto Exterior, Horta e Costa and Central districts as well as the Hengqin campus of the University of Macao.

The incident was caused by a malfunction occurred in high voltage equipment at the Canal Dos Patos substation, which also affected four other substations, said the director of Energy Sector Development Office Arnaldo Santos in the press release, adding that the power supply in these four stations had begun to restore at about 12:20 p.m. (0420 GMT).

Macao's power supplier is asked to look into the cause of the power failure and to submit preliminary investigation report within a week, and present a detailed report in one month based on the contract, the director said at the meeting.

The power company director Bernie Leong expressed regret to Macao residents, saying the incident is rare. He noted that the power outage has nothing to do with the power supply from the mainland, adding the power grid in Macao is stable, and they can ensure the security of power supply.

The power failure was a severe one since Macao's return to motherland, causing trouble to citizens and paralyzing the fixed- line telephone. Seventy-five cases of people stranded in lifts were reported and 13 units of traffic lights stopped working, said statistics from the fire department. Banking services and stores in the affected areas were also briefly suspended.