THE cause of the nasty niff that brought disruption to parts of Southampton yesterday is likely to remain a mystery.

More than 300 worried people bombarded gas firm Transco with calls after noticing a strong smell of gas in the city centre.

The crown court had to be evacuated and remained closed for most of the day, with all civil cases transferred to the neighbouring magistrates court while criminal proceedings were adjourned for the day.

Police and fire services were put on alert at 9.45am but were stood down when a team of 50 engineers from Transco were drafted in to try to find what was causing the pong.

But in spite of an all-day probe, experts could not pinpoint what had caused the smell which could be detected in Millbrook, Shirley and the docks.

Engineers from the firm tested the odour but later confirmed it was not natural gas.

Early suspicions that it came from Fawley refinery were also dismissed by a spokesman who said all necessary tests had been carried out.

Environmental health bosses at the city council also launched an investigation but admitted that its origins could well remain a mystery.

They blamed unusual weather conditions yesterday which trapped the smell in Southampton.

Phil Wells pollution and safety services manager at the council said that the lack of wind and low temperatures had combined to keep the gas cloud over Southampton.

He said: "We are not doing much more unless it becomes a serious problem again.''