A school in northern Thailand where 17 girls were killed in a dormitory fire last week has reopened, but only about a third of the students returned because some families remain concerned about safety, a volunteer at the school said Tuesday.

Of the 142 students enrolled, fewer than 50 returned to classes Monday, said Thuenjai Thanachaikan, who helps out at the Pithakkaiat Witthaya School, located just outside the city of Chiang Rai.

She said parents were having a difficult time deciding whether to allow their children to return. Some have withdrawn their children from the school out of safety concerns.

The May 22 fire claimed the lives of 17 girls, aged 5 to 12, at the school, which provides free housing for impoverished children who are members of hill tribe minorities. Fifteen girls and a teacher escaped the fire by tying bedsheets together and using them to climb down from a second-floor window.

The bodies have been slowly returned to their families following DNA analysis to confirm their identities because many were burned beyond recognition.