China yesterday reported its first death of a person suffering from swine flu - but it remains unclear if the death was caused by the virus. Xinhua said a 34-year old female patient had been recovering - her temperature had been normal for a week and she had been coughing only occasionally while other symptoms were disappearing - when she died yesterday morning in a hospital in Xiaoshan Number One People's Hospital in Hanzhou city, Zhejiang province . The report said the patient was found dead in her ward toilet and described the death as accidental. She was admitted to hospital on June 23. The police are investigating the cause of death. So far it is unclear if the woman had any underlying disease and whether the death was caused by the virus. Meanwhile, a primary school in Beijing closed one week ahead of the summer holiday after 12 students in four different classes at the Nanhu Zhongyuan Primary School in Chaoyang district took sick leave on Monday due to fevers, alerting the city's Centre for Disease Prevention and Control. Those 12 students and another who had a sore throat were tested on Monday, and nine results came back positive on Tuesday. A further test confirmed that seven students were infected with swine flu, according to the Beijing Health Bureau. 'The municipal and district centres for disease prevention and control have set up an investigation team for a complete investigation to track down the infection source,' the bureau said. It had quarantined 93 students, 20 teachers and 41 parents, who had been in close contact with the patients, for observation. Other students and teachers were told to stay at home after the school closed early. The primary school, located in a residential area, has 941 students in 33 classes and 78 teachers. Local media reported that at least five children - two girls and three boys - at the school were taken away by ambulances early yesterday morning. The father of one girl who was taken away by ambulance said she developed a fever on Saturday but was described as being fine after a hospital check-up. The girl was asked to return to school late on Tuesday night and was then taken away by the health authorities. Shops and small restaurants near the school were asked to close, according to the Beijing Youth Daily. The bureau said the authorities would step up surveillance in schools and would carry out a city-wide inspection to make sure swine flu precautions were in place. The latest development came within one week of a similar outbreak at a primary school in Dongguan, Guangdong. Beijing yesterday reported 21 new cases, among a total of 57 on the mainland, which brought the total number of mainland infections to 867. More than 340 people are being treated in hospital and three others at home.