Police told of loud argument in flat The boyfriend of a mainland woman suffocated in her Kwai Chung home is being sought by police. Detectives believe a relationship problem was probably the motive behind the murder of 32-year-old Yang Xiuqiong. 'We are still making all efforts to find the killer,' Kwai Tsing district commander Chief Superintendent Kenny Ip Lau-chuen said last night. The manhunt began after the body of Yang was found in a third-floor flat of Kwai Fung House on Ping Lai Path on Wednesday. Police said the landlord had noticed a smell coming from the flat at about 7pm on Wednesday. When no one answered the door, he called the police. Officers and firemen broke into the room and found Yang's body on the floor. 'Her neck was tied by a curtain. She was certified dead at the scene,' a police spokesman said, adding the case had been classified as murder. Initial examination indicated Yang had been dead for more than 24 hours and an autopsy found she had been suffocated. Neighbours said they heard a heated argument in the flat a few days ago. Yang, who was separated from her Hong Kong husband, moved into the flat after she came from the mainland on a two-way permit. She has a 10-year-old son on the mainland. After learning of her death, Yang's parents and son came to Hong Kong yesterday from Danshui Guangdong. They were not allowed to enter the cordoned-off flat. The boy was seen gripping the security gate at the building's entrance crying and shouting for his mother late on Wednesday night. Her father also broke into tears. He was comforted by two plainclothes officers and later led away. Early yesterday, officers seized about 10 surveillance videotapes from the building. Boxes of evidence were seized and a mattress was also taken from the room. Before noon, Yang's son, mother and another female relative returned to Danshui. 'I missed my mother very much,' the boy told reporters after his return home. In Hong Kong, Yang's ex-husband said it was inappropriate to say anything during the investigation. Detectives from Kwai Chung district crime squad are investigating. No one has been arrested. The city has been rocked by a number of vicious murders this year, such as the beheading of 19-year-old Li Yui-yi in a Kwai Chung flat in March. In the middle of March, four sex workers were murdered in Yuen Long, Tai Po and North Point in three days. Police arrested two men. With those five deaths, 14 people were murdered in the city in the first quarter of the year, compared with three in the same period of last year.