Power surges to electricity cables under Buchanan Street left 115 properties without power - and sparked reports of explosions in Glasgow.
Fire crews were called to the scene on Tuesday at around 8am after reports of loud bangs and smoke.
Communters reported hearing two bangs and witnessed smoke rising from a drain close to the Apple shop.
An area at the junction with St Vincent Street was sealed off while firefighters investigated the cause and discovered there was a fault with an electrical cable about a metre underground.
Scottish Power workers were called to deal with the incident.
A company spokesman said said all properties affected had been re-connected by 09:25 and there was “no evidence of any explosion”.
A spokesman said: “We apologise for any inconvenience. We will now work to repair the cable fault.
“There was no evidence of any explosion. A bang was heard but the fault occurred several feet underground.”
Strathclyde Partnership for Transport said the situation “resulted in a power surge affecting signalling” on the city’s subway and warned of delays to services.
A spokeswoman for the service said: “We received a report of a bang coming from a drain in Buchanan Street.
“We requested Scottish Power. It was some electrical cables which Scottish Power have isolated.”
Twitter users described the incident as a “mini explosion”.
Nick Kewney tweeted: “Missed a mini explosion on Buchanan Street by about 5m! Nobody seems worried so guessing it’s a gas pipe.”
Police Scotland said there were reports of a power cut in the area and smoke coming from a drain.
The fire service said no fire had to be dealt with and the incident had been passed on to Scottish Power.