Undercover police posed as burglars to test the effectiveness of caretakers - and found most let them walk straight in. In response to a rise in burglaries in Mongkok, 50 police posed as thieves to see if doormen were making life too easy for criminals. They rang doorbells and tried following residents into 102 offices and residential apartment blocks, and were challenged by caretakers in only 44. 'Seven buildings had no caretakers at all. Others just let them in without inquiring about them although they obviously noticed they were strangers,' a police spokesman said. 'In one case the undercover officer said he wanted to go to the 15th floor even though the building only had 13 floors. But even so, he was still allowed into the lift.' There were 250 reported burglaries in Mongkok in the first four months of the year, a 30 per cent rise on the same period last year. After the two-day operation, security guards at 29 buildings were issued with written warnings and 22 were given verbal warnings. Mongkok police also gave commendations to 13 caretakers. Caretaker Wong Ai-ching, who is in her 50s, spotted a stranger - one of the undercover officers - last week as soon as he entered her building. She asked which floor he was visiting and told him to produce his ID card. She called for help when the officer tried to cause trouble.