Immigration police swooped in a twilight raid on an Oxford warehouse as part of a clampdown on illegal workers.

A team of officers from the Government's UK Border Agency struck at Smiths News Plc on the Horspath Industrial Estate, in Peterley Road, Cowley, at 3am today and arrested two people.

Smiths News stressed tonight workers arrested in the raid were not employed by the firm and were "self-employed contractors".

A spokesman also insisted the company had "rigorous controls" to make sure staff had the right to work in the UK.

The raid was carried out after a month's surveillance at the site and officers entered the building armed with batons.

Smiths News is a national firm, which distributes newspapers, with about 30 people working in Cowley.

Everyone working at the warehouse was detained and their identities checked while officers searched possible hiding places.

Delivery driver Shakheel Ahmed, from Cowley, said: "I had just come to work and suddenly it happened.

"There were so many cars and vans. They rounded us up and said everyone come to the warehouse.

"It has never happened before. It was scary. Everybody was shocked."

Officers had confiscated knives used for cutting bundles of newspapers and arrested two men under the 1971 Immigration Act.

A 35-year-old man from Pakistan was arrested on suspicion of working illegally.

A 40-year-old Brazilian was arrested on ID card offences after he showed officers what was believed to be a forged Portuguese driving licence.

Officers then raided a house in Clive Road, Cowley, where they found a 29-year-old South African woman who had overstayed her visa.

Alex Legg, chief immigration officer for West London and the Thames Valley, said colleagues would arrange for her to catch a flight home as soon as possible.

He said the man from Pakistan would be sent home within a week, while the Brazilian would probably face criminal charges for having a false document.

The night manager of the depot was also handed a Notice of Potential Liability — meaning Smiths News could be fined £10,000 for each worker whose application was not checked properly.

Mr Legg said: "I am happy with the operation. It was over quickly and contained well on arrival. It will give out the message that we will no longer tolerate illegal working in our community."

Glenn Leech, from Smiths News, said: "We take the issue of immigration law very seriously and have rigorous controls to ensure our employees are eligible to work in the UK. "On visiting our premises at Oxford, the authorities found two self-employed contractors who did not have the paperwork to support their right to work.

"We would like to stress that the two people identified are not employed by Smiths News. "Across our business, we use a large number of contractors. As a responsible company, we give guidelines to help contractors comply with the law and we have very few issues of this nature."

Gareth Redmond, UK Border Agency area director, said: "These arrests send a clear message to businesses in Cowley. We will not tolerate illegal working in Oxfordshire."

The operation follows two other raids on Smiths News warehouses in Slough and Hammersmith.