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.
Police in London also arrested six people Thursday on suspicion of committing, planning or instigating terror offenses. Those arrests were not related to the Olympic or Paralympic Games, police said.
The arrests announced Friday involve six men from the West Midlands, all in their 20s, and a 43-year-old man from West Yorkshire.
The seven men have been detained on suspicion of the commission, preparation or instigation of acts of terrorism, a police statement said.
Detective Chief Supt. Kenny Bell of the West Midlands Counter Terrorism Unit said: "As soon as the items were discovered in the impounded vehicle, our priority was to protect the public by pursuing and arresting those we believed to be involved."
The firearms, which were not loaded when they were found, are being tested, and police are searching a number of addresses, the statement said.
No information has yet been given on the motivation of the suspects.
However, it is understood that the individuals arrested in the West Midlands and West Yorkshire were not targeting the Olympics, nor did they have any links to those arrested Thursday in London.
Following these arrests the UK Home Office website has not changed the terror threat level from "substantial," which is the third highest of five levels. The next level up is "severe," which means an attack is "highly likely," and the highest is "critical," meaning an attack is "expected imminently."
Additional security measures will be in place in London and elsewhere during the Olympics.
They include the siting of missile defense systems around the capital and fighter jets on standby at air bases close to London. Police and intelligence agencies have also stepped up monitoring efforts.
Government officials from Washington to London insist there are no known specific or credible terror threats tied to the Olympics. Nonetheless, authorities on both sides of the Atlantic are urging vigilance.
The Metropolitan Police is leading the "largest peacetime operation" seen in the United Kingdom as it seeks to keep the public safe, it said, with up to 9,500 police officers from London and elsewhere to be deployed on the busiest days of the Olympics.
As a result, London's residents and its visitors can expect to see a large police presence on the streets and airport-style security at Olympic venues.
The driver of the bus caught up in Thursday's terror alert on the M6 Toll motorway was praised by his company, Megabus, in a statement Friday for his "calm and professional" response to the incident.
"It was a scary thing for a lot of people and it was a very long and tiring day," the driver is quoted as saying. "We were all in it together and when you're faced with armed police you can't really do anything else other than follow their instructions."
CNN's Laura Perez Maestro and Jonathan Wald contributed to this report.