A primary school teacher described as devoted and hardworking killed herself by burning charcoal in her To Kwa Wan flat yesterday after leaving a suicide note apologising to her pupils. Maths teacher Karen Li Wai, 25, failed to appear for work at the Shun Tak Fraternal Association Leung Kit Wah Primary School in Tseung Kwan O on Monday, setting off a search by the school and her relatives. Her mother, Leung Wing-chun, 50, also tried to locate her after being told by the school that she was missing. Ms Leung went to the sixth-floor flat in Ma Tau Wai Road, To Kwa Wan, where Li lived alone. When no one answered the door, she called in emergency crews. Li was found unconscious on the bathroom floor next to a pot containing charcoal ash. She was taken to Queen Elizabeth Hospital where she was declared dead. In a suicide note found in the flat, Li apologised to her family and boyfriend and her pupils. A police spokeswoman said the note did not explain why Li took her own life. The teacher graduated from Chinese University in 2000 and started working at the primary school last September. Li, who was a Primary Five teacher, mainly taught mathematics, but also took classes in Chinese, Putonghua and general knowledge. Principal Chan Yam-cheong said Li's death had left colleagues and pupils in a state of shock. He said many of her pupils burst into tears after hearing the news and some needed counselling by educational psychologists. 'She was a young teacher but she was hardworking, responsible and devoted to teaching. Her performance was good. She had a good relationship with other teachers and she was well-liked by her students. We are shocked by her death,' he said. Mr Chan said Li's workload was average and she did not have any job-related problems. 'At the beginning of the school year, she had talked to us about having work-related stress, but she later adapted. She was always happy and smiling when she chatted with other teachers and students.' Li is the second teacher to commit suicide this academic year. Award-winning Yeung Yiu-shing, 42, who was suffering from work-related depression, jumped to his death from a public housing block in Sha Tin in September. Yeung, who taught at Lingnan Dr Chung Wing Kwong Memorial Secondary School in Kwai Chung for 21 years, was described by the principal as a 'perfectionist and workaholic'. Early last year he was presented with an outstanding teacher award under the 2000 Teachers Commendation Scheme. Hotline numbers for people contemplating suicide: Samaritan Befrienders (Cantonese) 2389 2222. Samaritans (multilingual) 2896 0000.