Power has been restored in the Melbourne suburbs of Southbank and South Melbourne after an outage that affected 10,000 people, provider Citipower says.

Citipower said the outage was caused by two linked substations going down in South Melbourne and Southbank.

Citipower spokesman Drew Douglas said one of the lines supplying power from the substations was down due to planned maintenance when the second back-up line went down.

He said the second line appeared to have been taken out in a traffic incident, but the official cause was still under investigation.

A large number of traffic signals were affected by the power failure and VicRoads urged motorists to approach intersections with care.

Melbourne Arts Centre was evacuated as a result of the outage.

Citipower said electricity was restored at 11:33am, despite an earlier warning that the outage could last until 1:00pm.