Metro has apologised to passengers impacted by a power outage in the City Loop.

Commuters spent up to 45 minutes trapped on trains in complete darkness on Wednesday morning after a power failure in the loop.

The loss of power affected the part of the loop that carries Craigieburn, Sunbury, and Upfield lines.

Metro CEO Mike Houghton told Nick McCallum said this has never happened in the loop before.

‘These failures are very rare,’ Mr Houghton said.

‘When they do occur, they’re a safe failure, in that they don’t cause any safety risk.’

Affected passengers can apply for compensation by calling 1800 800 007.

Power has since been restored.

Click play to hear from Mike Houghton on 3AW Drive