A serious gas leakon the A6120 Ring Road (Horsforth New Road), near Calverley Bridge, has caused traffic disruption across West Leeds.
Northern Gas Networks have said they will be carrying extensive works to rectify the emergency.
A Leeds City Council highways officer said: “This is a medium pressure 12-inch metal gas pipe and Northern Gas Networks have been investigating the gas leak and made site safe, which has involved reducing the pressure to a safe level.
“They are going to set up two-way lights to allow safe excavation and carry out the repair. Works will continue overnight until the main is made safe and the temporary traffic lights will be manually operated when in use.
“Due to the busy location, major delays are expected, especially during the busy periods, however Northern Gas Networks and ourselves will do everything possible to reduce this and get the lights removed as soon as possible.”