A section of a main road in Swindon has been closed due to a gas leak, police said.
Wiltshire Police received a report of a gas leak near to Toys 'R' Us by the A420 shortly after 6am on Saturday.
The road has been closed from the White Hart roundabout, past Gablecoss Police Station and up to Watchfield.
Engineers are at the scene, but work is expected to last for several hours.
Superintendent Phil Staynings, of Wiltshire Police, said: "We received a number of calls relating to this gas leak this morning and we are on scene, along with representatives from the gas company and colleagues from the fire service.
"Specialist engineers are hoping to make the scene safe as soon as possible.
"We appreciate this is a major road and as a result there are likely to be long delays in the area so we would urge drivers to seek an alternative route where possible.
"Business is continuing as normal for officers based at Gablecross and we are responding to emergency calls as we normally would."
Thara Raj, consultant in Health Protection for Public Health England, said: "The highest risk of natural gas exposure is suffocation in confined environments, and because the leak is outdoors this is not a risk.
"Repairs are being made to the affected pipe to minimise risk of explosion and risks to public health are low.
"In the unlikely occurrence that individuals develop symptoms, we would advise that they contact NHS 111 for medical advice."