Immigration officers swooped on a Wembley business arresting a number of employees working in the country illegally.
Nine unmarked vans containing about 30 officers from the UK Border Agency raided the warehouse of Euro Car Parts, in Fulton Road, yesterday morning after a tip-off that illegal immigrants were earning a living at the company.
More than 100 employees of the car part distribution firm were rounded up on its large industrial site, as the immigration enforcers streamed in and secured a number of entrances and exits.
Police dogs then searched the grounds to locate any workers hiding in the delivery van forecourt, customer car park, and vast warehouse where the company stored its merchandise.
Identification checks were then carried out to determine who could legally work in the UK and those who had fake and invalid documents and visas.
As the Observer went to press five people from Brazil, Columbia and India had been arrested and a further 12 people were being interrogated to determine if they had permission to work in the country.
Chief Immigration Officer, Alex Legg, said he was happy with the operation.
"It was a very large site and was very challenging to secure, but we did it quickly and effectively.
"We will now serve a notice to the employer asking him to provide documentation that all pre-employment procedures were in place to ensure its staff were working legally. If he fails to do this the company is liable for a s10,000 fine per immigrant."
The members of staff from Britain and the EU, who had valid identification documents, were allowed to continue working, while officers interviewed the people they suspected of flouting immigration laws.
Some were put through a fingerprint recognition system to determine if they were giving their true name and details.
The Indian worker was arrested for overstaying his visa expiry date and two Brazilian men and a Colombian were found to be in the country illegally.
The final man who was detained claimed to be Italian, but Home Office checks revealed he was a Brazilan who had a student visa that did not entitle him to work full-time.
Border Agency spokesman Stephen Carter, said the onus was on companies to make sure its staff had all the correct documentation to work in the UK.
He said: "Our argument is that if there were not any illegal jobs in the UK there would not be illegal immigrants coming here."
The workers with fake documents were taken to police stations and the ones who had overstayed their welcome were taken to Home Office detention centres and face being sent back to their own countries.
The UK Border Agency, which is part of the Home Office, carries out around 50 raids in London every week.