A nighttime fire at a dormitory of a primary school in northern Thailand killed 18 girls, many of whom had been roused by a dorm-mate but went back to sleep, thinking it was a prank, officials and the girl who sounded the alarm said Monday. The victims were between 5 and 12 years old. Five girls were injured in the Sunday night fire. Many survived by rappelling down from a second-floor window using sheets tied together to form a rope. The two-storey wooden structure that caught fire housed 38 girls, most of them belonging to the area’s ethnic minorities. Fifteen girls escaped without injuries. The cause of the fire was not immediately known. Death toll rises to 18 in elementary school dorm fire in Chiang Rai, #Thailand . 20 girls rescued, 5 of them injured. pic.twitter.com/vPJdmEmrZw — Steve Herman (@W7VOA) May 23, 2016 <!--//--><![CDATA[// ><!--\n\n\n//--><!]]> Some of the students were still not asleep when the fire broke out and were able to raise the alarm, said Rewat Wassana, manager of the Pithakkaiat Witthaya School, to which the dorm is attached. The kindergarten and primary school in Wiang Pa Pao district, just outside the city of Chiang Rai, has about 400 day students and boarders. It is about 800 kilometres north of Bangkok. Rewat said the fire broke out in the dorm’s lower level, which is used for activities. The upper level housed the sleeping quarters. It is one of the two dorms on the school grounds. The other dorm, which is located nearby and is for boys, was untouched, Rewat said. “We have a teacher who sleeps with the girls in the dorm. She tried to help the students escape,” Rewat told reporters at a news conference broadcast on local television. An 11-year-old girl identified only as Suchada said at the same news conference that she had gotten up to go to the bathroom when she noticed the fire downstairs, and ran to tell her friends in various rooms. But some of them didn’t believe her and closed the door on her to go back to sleep, she said. “We remembered some lessons from Girl Scouts to tie cloth together to make a long rope and we climbed out of the window,” the fifth-grade student said. “The teacher helped us. While the teacher was climbing down, the rope tore and she hurt her leg and waist.” A police official said besides the 18 dead, another five girls were injured, including two in serious condition. He said two of the bodies were so badly burned they were unidentifiable. Firefighters took three hours to extinguish the fire, and pulled survivors and bodies from the second-story window of the wooden building. Chiang Rai town and the surrounding hills are popular with foreign tourists for hiking and adventure sports. Visitors can go on tours to see the isolated tribes, although the practice of taking posed photographs at villages has come in for criticism. Thailand has poor health and safety standards and accidents are common across the kingdom.