Many Sheffield residents took to social media last night to complain about a mysterious 'loud noise' above the city.
Woodhouse residents said they were woken at around 2am by a 'horrendously loud noise' near the train station.
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Many said they thought at first it could have been a helicopter circling above but others suggested the noise could have been coming from a train on the railway.
Woodhouse train station was reportedly lit up last night, leaving some residents to suggest that they were conducting track maintenance.
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Jodi Booker said: "I opened my door and could hear what sounded like metal grinding as well as the whirring so maybe it is something to do with the line?"
Karl Hammond said: "It was track maintenance. I saw what looked like a train going up and down the track from Woodhouse train station..it woke me up."
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The noise could reportedly be heard as far as Darnall while some residents have said they have heard the noise for the past three nights.
High Output teams at Network Rail often replace tracks overnight using an 'efficient track relaying system'.