Tokyo police on Saturday said that an arrest warrant for arson has been served to the high school student suspected of killing a female schoolmate and torching her apartment in Taito Ward last month.
The new warrant was served to renew the 18-year-old's legal detention period, which had expired while prosecutors were investigating him. In Japan, suspects must be released after 23 days unless charged.
The teen has been silent during questioning and prosecutors have been stumped on whether to indict him for murder.
According to the police, the teen, whose name is being withheld because he is a minor, is suspected of setting fire to a room in the apartment of 17-year-old Mai Sato in Taito Ward sometime within 12 hours of 8:30 p.m. on May 3. The pair had been dating.
In voluntary questioning before he was initially arrested on May 13 on suspicion of murder, the teen told the police that he "set fire to a quilt with a lighter" in the second-floor apartment.
According to the police, the girl was found on her back beside the quilt. The blaze damaged more than 30 sq. meters of the unit, including the floor and walls, and several lighters were found at the scene.
He became a suspect after alerting the police about the fire at around 8:35 a.m. on May 4. Sato was pronounced dead at a hospital following the fire.
The police said that shortly after he was arrested, the teen admitted to choking Sato with his hands. They also suspect him of trying to drown her in a bath tub and then lighting the room on fire with her body in it to make her death look like an accident, because water was found in Sato's lungs.