Five fire crews and a command unit closed off Hanover and Filleul Sts after they were called about 11.30am.
Dunedin Central senior station officer Justin Wafer said while investigating, crews came across heavy smoke from the melted switchboard.
He said the cause was a component failure in the main electrical switchboard located on the upper level of the mall.
"A command unit was called ... as part of an automatic response to a second alarm sounding during a fire in the centre city", he said.
Mr Wafer said the fault was quickly sorted out.
"There was no actual fire — overheating causing significant heavy smoke."
A Fire and Emergency New Zealand spokeswoman said the incident was contained by 12.40pm and over by 1.10pm.
Breathing apparatus was used as a precaution.
Crews from Dunedin Central, Roslyn and Willowbank attended.
