London (CNN) -- Seven men have been arrested in the United Kingdom on suspicion of terror offenses, West Midlands police said Friday. The arrests on Tuesday, Wednesday and Thursday followed the discovery of two guns and a small amount of ammunition hidden in a car stopped by police last weekend who believed it was uninsured, the police said. The news comes as Britain is in a state of heightened security ahead of the London Olympics, which open in three weeks. On Thursday, armed police in Staffordshire closed a major highway and called in bomb disposal squads when a passenger on a bus raised the alarm over smoke coming from a fellow traveler's bag. The source turned out to be a quit-smoking aid, and no arrests were made.
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NEW: Police found two unloaded guns and some ammunition in a car they stopped
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Six men were arrested in the West Midlands and one in West Yorkshire, police say
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The UK Home Office terror threat level remains unchanged, at "substantial"
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Security has been stepped up in Britain ahead of the Olympic Games
Additional security measures will be in place in London and elsewhere during the @placeholder.