Drivers reported seeing a plume of gas fumes shooting into the air from a nearby field before a sickening smell enveloped the motorway.
The problem was caused by a fault in the gas main which runs under the field near the Maryville Interchange, just off Junction 1 of the M73 at Uddingston..
Drivers described the smell of gas as "horrific" and took to social networking sites to warn other motorists.
Concerned drivers alerted the Scottish Fire Service to the strong smell of gas.
Police and fire crews rushed to the scene at around 1pm yesterday.
Scottish Gas Networks said engineers had located the leak and were working through the afternoon to fix the fault.
One motorist said a strong smell of gas was in the air as far away as Blantyre.
Police were slowing traffic at the scene, behind the Bargeddie Industrial Estate, and only allowing lines of around 20 cars to pass at any one time.
The driver said: "We were heading out from Glasgow and you could smell the gas all the way from Blantyre.
"The roar of the escaping gas is really loud as well - I haven't heard anything like that before.
"Traffic is not as bad as I would expect but it is moving very slowly and holding people up."
Other motorists took to Twitter to share their concerns.
One man tweeted: "The smell of gas making me sick driving along the M73."
A woman also wrote: "Any news re gas leak on M73? Fire brigade everywhere and the smell is horrific."
A spokesman for Scottish Gas Networks later confirmed the leak had been located beneath a field adjacent to the motorway.
He said: "Our engineers are on site and we're working to resolve the situation as quickly and safely as possible."
The spokesman said there had been no official evacuations linked to the incident.
A spokeswoman for Police Scotland confirmed officers were at the scene.
The Scottish Fire and Rescue Service said three appliances and the Environmental Protection Team from Hamilton were also at the site during the incident.
The motorway was believed to be down to one lane yesterday afternoon while staff carried out an inspection of the area.