A suspicious powder brought Wolverhampton’s Royal Mail delivery and sorting office to a standstill.

No-one was allowed in or out of the city’s Sun Street mail centre,  which deals with more than 13million items per week, after a suspicious powder spilled out of a package at around 8pm last night. It is believed the substance discovered was a type of aluminium sulphate.

The problem has caused a “small proportion” of mail being posted out to areas other than Stoke-on-Trent, Dudley, Walsall and Wolverhampton to be delayed. Three workers also had to be decontaminated as a precaution.

Firefighters, ambulance staff and police all attended the busy base to investigate the incident with West Midlands Ambulance Service sending its Hazardous Area Response Team.

Many workers at the base turned up for an evening shift only to be asked to wait outside while investigations continued. They were allowed back in shortly after 10pm. ]

One worker who was stuck inside said: “It was a bit of a surprise to us but we were glad when it was all over.”

Royal Mail spokesman Mike Dalton said: “A suspect powder spilled out of a package which was going through the sorting system. We followed advice from the emergency services and rather than evacuate the building we didn’t let anyone in or out.

“Three individuals who came into direct contact with it were isolated. The substance was checked and found not to pose a risk, but the three individuals were decontaminated as a precaution.”

The drama caused heavy traffic in Sun Street as staff turning up to work were held up. Two Royal Mail lorries were among vehicles forced to park up and wait.