Firefighters have been called to a gas leak on Stacey Street near the junction of Shaftesbury Avenue.
A 50-metre cordon is in place and around 30 people have been evacuated from three surrounding properties as a precaution. There are no reports of any injuries.
Station Commander Daniel Perrett, who is at the scene, said: "Crews are working with partners to isolate a gas main which has ruptured and make the scene safe.
"The incident is expected to be protracted and there are road closures in place, which are causing some disruption. We encourage people to avoid the area where possible.
"A rest centre has been established to support affected local residents as we work to resolve the incident."
The Brigade was called at 1331 and three fire engines and two command units from Soho, Euston, Bethnal Green and Dowgate fire stations are at the scene.