A teacher at a Tokyo elementary school where a fire broke out last week has said she was drying laundry in a room to store musical instruments, police sources said Wednesday.

Tokyo’s Metropolitan Police Department is investigating a possible causal link between the teacher’s explanation and the fire at Takinogawa Daisan Elementary School in Kita Ward that left 11 people injured, on suspicion of negligent fire-setting.

In a voluntary hearing on Tuesday, the teacher in her 40s said that she was drying laundry in the storage room on the fourth floor of the school, using air circulators, the police said.

She asked whether children and other teachers were safe, showing how sorry she was, according to the police. The investigators will continue to hear from her as a person of interest.

In addition to a burnt electric heater and multiple air circulators, a power strip with multiple outlets was found at the scene.

An examination after dismantling the electric heater found that it was likely energized when the fire started. The police found something like fibers sticking to a fragment of the wreckage. Whether the heater was on at that time is unknown, according to the police.

The fire started at around 11 a.m. on Friday, burning some 200 square meters, including a music room next to the storage room.

Children who were taking a class in the music room evacuated to the ledge of the building, which has a width of about 80 centimeters, outside the windows.

A boy and the teacher broke bones from falling after exiting the windows, while seven students and two teachers suffered smoke inhalation.