At least 29 people have been killed in a hospital fire in the <a href="https://www.thenationalnews.com/tags/china/" target="_blank">Chinese</a> capital of <a href="https://www.thenationalnews.com/tags/beijing/" target="_blank">Beijing</a> — with survivors forced to jump out of windows to escape — state news agency Xinhua reported on Wednesday. The fire at the private Changfeng Hospital broke out on Tuesday and had been extinguished by mid-afternoon local time on Wednesday, it said. Dozens were forced to flee the building, while some of those who were trapped escaped from windows using bedsheets tied together. Those killed were 26 patients, a nurse, a medical assistant and a patient's family member, said Li Zongrong, deputy head of the Fengtai district. An investigation is under way to determine the cause of the fire, which officials believe was started by welding sparks from work in the hospital’s inpatient wing. Twelve people, including the hospital’s head and her deputy, have been arrested, as has the chief of the construction crew. The Fengtai district's deputy mayor expressed his "deep condolences" over the deaths of the 16 women and 13 men killed in the inferno. "We feel deep remorse and guilt," Li Zongrong said on Wednesday. "I hereby express our deep condolences for the victims, and express our sincere respects to the victims' families, the injured and their relatives, and apologise to the people of the whole city." Beijing party secretary Yin Li vowed to "quickly identify the cause of the accident and hold the relevant responsible persons accountable", according to the <i>Beijing Daily</i>. At least 39 people were injured in the fire, three of them are in critical condition, according to authorities. Rescue crews and medical staff from around the city were mobilised, with squads plucking some of the 142 people who were rescued from air-conditioning units on the building's exterior. The hospital is in the capital's western urban area, about 25 minutes by car from Tiananmen Square. Fatal fires are common in China because of weak safety standards and lax enforcement of regulations. It was the deadliest blaze in Beijing for more than two decades. Since an explosion in 2015 at a chemical warehouse killed 173 people in the northern port city of Tianjin, Chinese officials have pledged stronger safety measures. The majority of people that died were mostly firefighters and police officers. Another fire in 2002 at an internet cafe killed 25 students.