A mainland gang used discarded junk - including umbrellas, radio antennas and plastic bottles - to conduct a series of break-ins in Kowloon City which netted valuables worth more than $50,000. They used socks as gloves and carried miniature torches and were able to complete the burglaries without waking the sleeping victims, according to police. Over the past two days, police have arrested seven mainlanders travelling on tourist visas, who all came from the same town. Makeshift tools and $6,000 worth of stolen property were seized. Chief Inspector Eric Chung Chi-ming of Kowloon City police station said the seven men aged between 23 and 38 were thought responsible for at least six burglaries in the district since Friday. He said up to $50,000 worth of valuables such as diamond rings, watches and mobile phones were stolen in the six break-ins. Last night, officers were still investigating whether the suspects had Hong Kong connections to sell the goods. Police said the suspects worked in pairs and struck early in the morning. 'Their tactics were very simple. They targeted old buildings with no security guards, no surveillance cameras,' Mr Chung said. 'They lowered an umbrella frame or extendable antenna from outside to the latch of a security gate and then unlocked the gate by pulling the lock's handle,' he added. 'They cut plastic squares from bottles and wedged them into the gap between the door and door frame to unlock it.' He said they even entered bedrooms to search for valuables, but never disturbed sleeping tenants. 'Some tenants might not be aware their units had been burgled because no damage was done to the door or security gate.' Detectives began their investigations after a sharp rise in the number of similar break-ins in the district last month. Assistant Kowloon City district commander (Crime) Superintendent Yam Chiu-fan said there had been about 15 since June. About 30 plain-clothes officers recently started staking out the old buildings. One of the suspects was arrested in Carpenter Road, Kowloon City, at about 3am on Monday. Six men were arrested between 3.30am and 4.30am on Tuesday. Last night, the seven men were being held for questioning.