Bucks Fire and Rescue received 15 calls about the incident with some callers reporting hearing an explosion.
A fire service spokesman said the explosion was caused by an underground electrical fuse board located in the pavement.
Part of Buckingham Street is cordoned off while ten firefighters tackle the incident with a dry powder extinguisher and a PPV fan.
The spokesman added: “We believe some nearby buildings may have lost their electricity supply as a result of the incident.
“There is some damage to the manhole cover and the pavement and also to an advertising sign.
“Part of the road is cordoned off and we are now waiting for the electricity company to arrive.”