A mass power shutdown across Melbourne's CBD triggered by a burst water main has caused peak-hour chaos in the heart of the city.

Around 10,000 customers in the city's south-east were impacted and dozens of traffic lights in the area went dark after the water flooded a carpark on Little Collins Street, a Citipower spokesperson has confirmed.

The water entered a substation in the basement, resulting in the power being cut in the CBD for safety reasons.

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https://x.com/victraffic/status/2058803582577594825?s=46&t=MXsRfXf2kIIGsKchE0jYnA

The site provides power to around 10,000 people in the south-eastern area of Melbourne's CBD.

According to CitiPower, around 5700 customers were without power as of 5.30pm.

"We have been able to restore power to more than 4000 customers by redirecting power supply from other parts of the network," a spokesperson said.

Up to 40 sets of traffic lights across the city centre, East Melbourne and South Yarra are without power, according to VicTraffic.

Drivers have been warned to stay alert in the impacted suburbs.

Some Metro train lines have also been delayed by the power shut-off.

"Our crews are on site and working to remove the water so they can safely access the zone substation and assess any damage," the spokesperson added.

"We will keep customers updated by SMS and on our website on restoration times."

More to come.