A "BIZARRE and mysterious" noise has been keeping Southampton residents awake.

People living near Southampton General Hospital first heard the very loud "wooshing" noise, which was described as sounding similar to a "steam train", at about 9.30pm last night – it went on until around 1.30am.

Caroline Snook, 36, of Outer Circle, said she had lived in her home six-and-a-half-years and had never heard anything like it.

She added her neighbours also heard the noise as well as other residents in Palm Road.

"We get helicopters around here all the time so when we first heard it I didn't think much about it but when it went on for more than an hour we looked out the window and saw lots of steam being shot out into the air, like pressure being released from somewhere,” she said.

"It looked like it was coming from near the hospital. I have never seen anything like it.

"It was really weird and just bizarre. It could have just been something routine but I have lived here six-and-a-half-years and have never heard anything like it.

"When it stopped everything just went deafeningly silent....There must be an explanation."