Firefighters were called to a gas leak on Seething Lane in The City of London.
A 24-inch gas main ruptured, causing gas to leak into a nearby basement.
Crews worked with the gas authority to extract and ventilate the gas to open air. Around 1300 people were evacuated from residential properties, a hotel and local offices and a 25-metre cordon was put in place as a precaution. There were no reports of any injuries.
Firefighters carried out a sweep of the surrounding area to check for elevated readings of gas and confirmed no elevated readings remained.
The Brigade was called at 1447 and the incident was over for firefighters by 2139. Fire crews from Whitechapel, Dowgate, Paddington and surrounding fire stations attended the scene.