Fire crews from Leyland and Penwortham were called to the incident on Liverpool Road, Walmer Bridge just after 2pm on Friday, November 24.
A trailer had detached from a vehicle and sheared a gas main, the fire service said.
Around 40 homes have had to be evacuated and a nearby village hall has been set up as an emergency shelter.
A South Ribble Council spokesman said: "The village hall on Boundary Close, New Longton has been opened as a temporary shelter/rest centre for residents evacuated/unable to return home due to a gas leak in Walmer Bridge."Residents should make their way directly to the rest centre so they can shelter and receive updates".Lancashire Police has warned people to avoid the area.
They said: "We are at the scene of a gas leak on Liverpool Road, Walmer Bridge with Lancashire Fire and Rescue. A number of properties have been evacuated. Please avoid the area. More information to follow."
Gas engineers are currently on the scene attempting to repair the damage.