Emergency services are responding to a major gas leak at Cumberland Park that has forced the evacuation of dozens of surrounding homes in Adelaide's inner south.
Metropolitan Fire Service (MFS) crews were called to the corner of Cross Road and Hill Avenue about 12:50am.
About 40 homes were evacuated after residents within a 100-metre radius of the leak were awoken by police in the middle of the night and told to leave the area.
SA Water spokesman Joshua Zugajev said crews installing a new water main on Cross Road "accidentally made contact with a gas main".
He apologised to the residents who had to leave their homes.
"The information that I have is that the required checks were completed before work was done to understand where there were any underground assets, but sometimes, as we find dealing with underground infrastructure, there can be slight differences with the plan and what was actually built," he said.
Firefighters knocked on doors to tell residents to leave.
All but one household had returned to their homes by midday.
"We had an exclusion zone set up and that included those original work crews — we moved everyone well away from the incident area just in case there was an ignition and a potential gas explosion," MFS station officer Graham Hughes told ABC Radio Adelaide.
A spokesperson said COVID-positive residents who had been isolating were among those evacuated, and were directed into their cars to ensure emergency service crews were not exposed.
Mr Hughes said there "was a lot of gas escaping" when crews first arrived.
"You could actually see the misting spray of the gas forcing itself out of the pipe," he said.
"A major gas main has been damaged, the line that runs down Cross Road has been ruptured.
"It's a major junction point and there's going to be significant gas supply issues today.
"Gas is still flowing very freely, we're still dispersing [it] with our water lines and [the] gas company is still trying to work out what lines to shut down."
A truck had to be towed, rather than driven away from the scene, in order to avoid its ignition possibly sparking the gas.
Cross Road reopened about 11am after being closed in both directions between Winston Avenue and Goodwood Road from early in the morning.
"They were door-knocking every house in the street and they were in a hurry to get the message around that it was obviously pretty important to get out of there.
"We went out, came down the beach for a while, and then wandered back home but the smell of the gas near the house was just impossible.
"It was really overpowering, it was so bad you just had to get out of there."
Local resident Ellen lives 100 metres outside the exclusion zone.
She said the incident was "definitely a wake-up call" for someone in her situation.
"I'm also a deaf person and so I woke up this morning to the news feeling a bit shocked because I didn't know what was going on and I didn't know whether I was in danger or not in danger," she said.
"I guess I wouldn't have heard anyone knocking on my door at night-time then — because I live on my own, it definitely raised some concerns for me about how I would be alerted in a situation like that.
"I can get alarm bells that will shake the bed, for example. If someone knocks on the door then it will shake the bed but there's lots of little items I need to look into."
'We can't just turn it off'
General operations manager of the Australian Gas Networks, Mark Beech, said one gas line had been damaged but it was a major line that could not be simply switched off.
"We believe that a water contractor digging to repair a water main has damaged our main and caused a fairly significant gas escape," he said.
"The road will probably still remain blocked until about midday and there will probably be some traffic restriction on it for the rest of the day."
Mr Beech said the exact sequence of events in the lead-up to the rupture would be investigated.
About a dozen people congregated at a car park at a local shopping centre.
A major school in the vicinity, Cabra Dominican College, has been closed today and bus routes have also been impacted.
Principal Helen Riekie said online learning options were available to students.
"Our hope at the moment is that the matter will be resolved quickly and we'll be able to return to school tomorrow," she said.
