The incident occurred at Heysham 2, one of two nuclear power stations at the site near Heysham Port.
EDF said it was forced to shutdown one of its nuclear reactors (reactor 8) after an electrical fault disrupted its control system.
The energy giant said the incident happened late on Wednesday evening (August 14) and led to a complete shut down of the nuclear reactor.
EDF said loud noises which caused alarm in Heysham, Morecambe and Lancaster last night (Thursday, August 15) were caused by the nuclear reactor being 'restarted'.
Lancashire Police said it had been flooded with calls from locals concerned by the loud banging noise coming from the site.
An EDF spokesman said: "Yesterday afternoon we began the process of re-starting one of our reactors at Heysham 2 power station after an unplanned shut down.
"It can take a couple of days for a nuclear reactor to get restarted, and it's this process which caused some noise late last night (August 15).
"We appreciate that the noise can sound a bit alarming to those unfamiliar with the process, and this led to some speculation about its cause on social media.
"I would stress that the noise was completely normal for this kind of operation and we do apologise if this caused any alarm or caused any inconvenience.
"It is a routine process resulting from a minor issue with the control system's electrical supplies and the nuclear reactor is now back up and running."
The shutdown means Heysham 2's reactor 8 has ceased its world record-breaking run for the longest continuous operation of a nuclear generator without a shutdown.
On August 1, 2016, the reactor exceeded the previous world record of 894 days set by Pickering Nuclear Generating Station's Unit 7 in Lake Ontario, Canada in 1994.
More about Heysham Nuclear Power Station
- Heysham is the only site in the UK to have two operating nuclear power stations.
- Construction began in 1980 and first started generating nuclear energy in 1988
- Heysham is due to be decommissioned in 2030, when its energy-generating capability is expected to come to an end.
- Approximately 520 full time EDF Energy employees, plus over 250 full time contract staff work at the site
- In November 2018, three EDF employees were seriously injured in a steam leak at Heysham 1, prompting an investigation by the government's nuclear watchdog into safety standards at the site