Part of Oxford city centre was sealed off after a suspected chemical spill, causing disruption to thousands of workers and shoppers.

Rush-hour traffic was delayed as major routes, including Broad Street, Magdalen Street and Park End Street, were shut for nearly four hours.

Two police officers were taken to hospital for treatment after it was feared they had inhaled chemicals, but their condition was not serious.

The emergency was declared at 4.30pm yesterday after reports of a strong chemical smell coming from a white Transit van parked outside Debenhams in Magdalen Street. Firefighters, in protective clothing and wearing breathing apparatus, were sent to examine the unmarked van and its contents.

Emergency workers in Magdalen Street

They found about 50 containers inside. None was leaking but a vapour was being given off.

Divisional Fire Officer Ian Mills said: "Our normal procedure is to take the greatest level of protection we can for our people.

"They go into the area and get the information, and when they come out they have to be decontaminated as part of our procedure.

"There was not a chemical leak - something had been venting off."

The fire service remained at the scene until 8.30pm.

A fire service spokesman said the van's load was found to be "non hazardous" and the van driver was later allowed to take the vehicle away.

The van belonged to Didcot-based Capital Controls, which makes water analysis equipment. A spokesman for the company at the scene said the van should have been empty and he had no idea why it had been parked in Magdalen Street.

The harmless chemical, Tytronics Manganese, was described by police as being similar to vinegar, used for the testing of water purity.

The 26-year-old policeman and 29-year-old policewoman who were taken to hospital left after treatment.