Question: 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. Is Olympic-level security already under way in Britain? 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." Bus scare, terror arrests ramp up UK security concerns ahead of Olympics. CNN's Laura Perez Maestro and Jonathan Wald contributed to this report.
What are the important parts of this article?
Important parts: NEW: Police found two unloaded guns and some ammunition in a car they stopped. Six men were arrested in the West Midlands and one in West Yorkshire, police say. The UK Home Office terror threat level remains unchanged, at "substantial" Security has been stepped up in Britain ahead of the Olympic Games.

If you have ever struggled to untangle the wires on your headphones, an electrical extension cable or a reel of fishing line, then spare a thought for the workers at Britain's largest yarn processors who are responsible for keeping 1,500 miles of super-thin thread, tangle and snag-free each week. There has been a mill on the banks of the river Dove at Mayfield on the Staffordshire, Derbyshire border in Mayfield since the 1200's. Today thousands of spools and bobbins (known as cheeses), send the nylon and polyester yarn rushing along a labyrinth of frameworks – known as Creels – emerging to form giant webs that fan-out above the mill floor. They then feed into machines that use cameras and laser beams to constantly check up to 1000 threads at-a-time before the filaments contained in each thread are bonded in a glue and then dried. Workers at Britain's largest yarn processors who are responsible for keeping 1,500 miles of super-thin thread, tangle and snag-free each week. Machine Operator Ben Winfield checks the nylon and polyester yarn which is rushing along a labyrinth of frameworks – known as Creels. Warper Bryan Carter checks the 'cheeses' - the thousands of spools and bobbins which send the nylon and polyester yarn along frameworks. The 24-hour operation processes enough yarn each year to go around the world more than three times. Some of the yarns are so thin they are measured by weight with 10,000 thousand meters of some of today's threads weighing-in at only a few grams. Today's yarns are shipped to weaving companies around the world after being wound and twisted on one of the many machines that fill the other end of the factory floor. Mayfield Yarns supplies weavers who use the synthetic yarn to make highly technical and demanding fabrics such as automotive products, parachutes, sail cloth, hot air balloons and loading straps. Production operator Rob Waring 'tying-in' yarns -  the 24-hour operation processes enough yarn annually to go around the world three times. Some of the yarns are so thin they are measured by weight with 10,000 thousand meters of some threads weighing-in at only a few grams. The yarns are shipped to weaving companies around the world after being wound and twisted on one of the many machines in the factory. Mayfield Yarns supplies  yarn to make highly technical and demanding fabrics such as parachutes, sail cloth and hot air balloon straps. Bryan Carter, 59, has worked in the mill for 43 years - he is pictured after a giant spool of yarn was damaged in a customer's factory. There has been a mill on the banks of the river Dove at Mayfield on the Staffordshire, Derbyshire border in Mayfield since the 1200's.

Write highlights.

Workers at Britain's largest yarn processors keep 1,500 miles of thread tangle and snag-free each week. The super-thin synthetic fibres in nylon and polyester are used in everything from parachutes to sail cloth. The 24-hour operation processes enough yarn each year to go around the world more than three times. There has been a mill at Mayfield on the Staffordshire, Derbyshire border in Mayfield since the 1200's.