A 31-year-old woman was arrested Wednesday for allegedly killing her two-year-old son by wrapping a Japanese-style mattress called futon around him at their home in Tokyo, police said.

The mother, Haruka Takeda, has told investigators she wrapped Sotaro with the futon because he would not stop crying, but denied she meant to kill him. She said she had done so in the past when he would not stop crying.

The police suspect Sotaro died of suffocation, between 8:50 p.m. and 9:40 p.m. Tuesday.

Takeda was living with her husband, Sotaro and his twin sister at their home in Machida, Tokyo. The family was together when Sotaro began crying, and Takeda allegedly took him upstairs, wrapped him with the futon and left him.

The mother made an emergency call herself after realizing she did not hear Sotaro's voice, according to the police.