An odd smell is sweeping across much of Greater Manchester... but nobody knows what it is.
Gas board bosses have received more than 300 calls from people in Stockport, Tameside and Salford, complaining of an unpleasant pong.
Nobody knows what is causing it.
Hundreds of people said they could smell something like 'gas' in places including Denton, Redding, Gorton, Sale and Salford Quays on Tuesday.
Engineers attended and carried out safety checks. No problems were found with gas mains.
Cadent, which operates the gas distribution network across the region, said it doesn't know what is causing the smell, but urged people to keep reporting issues in case there is a leak.
Jane O'Driscoll, of Broadstone Road, Reddish, said she first caught a whiff in the early hours of Tuesday.
She said: "It is like a strong gas smell. I first smelt it when I went into garden to put my bins out but just thought it was my green food bin.
"Couldn't really smell it the next morning but it was very strong again last night and people had started to post about it."
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Dozens of people spoke about the incident on social media.
Some said they were initially told to keep windows and doors shut as tests were carried out.
One resident in Abbey Hey wrote: "My neighbours and I noticed a strong smell of gas in Ackroyd Avenue so phone the number to report it.
"They informed me that the smell has been reported in various places in Manchester. They have advised not use anything that can cause any form of ignition, keep windows and doors shut, and to take pets inside."
Another neighbour in Droylsden wrote: "The gas smell is a lot stronger tonight than last night. We phoned the emergency gas number last night for them to come out and check it out."
One person wrote: "Yes I smelt it when I come [sic] out of my friends in Gorton and it was bad all the way home to Clayton."
There were also reports of the smell in Salford Quays on Tuesday afternoon, Blackley, Unsworth, Whitefield, Clayton, Failsworth and Hyde.
A statement from Cadent read: "During yesterday Cadent, the local gas network, took approximately 300 calls from people in the Manchester area reporting a smell of gas.
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"Engineers investigated but did not find any gas leaks. The smell does not appear to be connected to Cadent’s network of underground gas pipes and gas equipment.
"The source of the smell has not yet been identified but the number of calls has dropped today.
"It is really important that if you think you smell gas you should always ring the National Gas Emergency Service. It’s always better to be safe than sorry."
If you smell gas call the National Gas Emergency number on 0800 111 999.
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