Contractors carrying out roadworks were to blame for a gas leak which led to dozens of people being evacuated from their homes.
According to an initial investigation into the leak on Oakbrook Road, in Nether Green, workers employed by Amey damaged gas equipment, forcing residents from their homes.
Those affected spent a day of uncertainty with no indication of when they might be allowed back into their properties.
Hundreds of people took refuge in Notre Dame High School and at Bramall Lane during the evening, on September 3.
Residents were finally allowed back into their homes at 11pm the same day – although many had already opted to stay in a hotel or with family and friends.
A spokesman for National Grid said: “We have carried out an initial investigation into this incident, which concluded that contractors working on the road damaged gas equipment, resulting in a gas escape.
“Our findings have been passed to the Health and Safety Executive.
“During the incident National Grid assisted the local authority which was providing alternative accommodation for those who needed it. National Grid was made aware of a small number of vulnerable residents who required overnight accommodation and we organised and paid for hotels for those residents.”
The Health and Safety Executive will now look into the incident.
Louise Wilcockson, who lives on Rustlings Road, said that the smell of gas was so strong she could still smell it in Greystones.
She said: “For the elderly and parents of small children that evening must have been a nightmare.
“Sheffield City Council’s Streets Ahead and Amey have never proactively acknowledged or apologised for this incident and I am sure people mistakenly think it must have been National Grid who caused it.
“I know there are people left out of pocket that day who had to stay out and bought things for an over-night stay – which looked extremely likely until we were allowed back around 11.30pm.”
An Amey spokesperson said: “The cause of the gas leak is currently being investigated by the Health and Safety Executive and their findings have not yet been confirmed.
“ We are cooperating with the on-going investigations and providing all requested information.”