Police raided the site and two other properties
Eleven people have been arrested as part of an investigation into a car repair garage in Southall.
The arrests were made when up to 75 officers raided Bray Engineering in Brent Road, Southall, and two properties in Guildford, Surrey.
A Metropolitan Police statement said the action was taken following a number of complaints from the public.
Alleged offences included assault, theft from motor vehicles, theft of motor vehicles and fraud.
About 30 people were working at the garage when police from the territorial support group turned up in six vehicles.
The raid also involved officers from Trading Standards, the UK Border Agency and the Department for Work and Pensions.
Garage owner Paul Dockerill, 45, and his son Martin, 23, both from Guildford, were arrested at the business premises.
Of those arrested two men were being held on suspicion of conspiracy to commit fraud, three on suspicion of assault, three over alleged immigration offences and one over suspected immigration and driving offences.
Det Ch Supt Andy Rowell said: "The level of complaints we have been receiving about this premises had to be acted upon.
"The allegations we have been investigating include threats of violence, intimidation and assault."
He said the operation had taken several months to plan and because the complaints had come from people across the country.
May 19th 2011