The suspect in the recent Kyoto animation studio arson was spotted at locations featured in one of its works for several days before the attack, investigative sources said Sunday.

Police are investigating the motives of Shinji Aoba, 41, for spreading and igniting gasoline at Kyoto Animation Co.'s three-story building on July 18 in an attack that left 35 people dead and many others injured. Aoba himself has severe burns as a result of the fire and remains in serious condition in hospital.

After arriving in Kyoto on July 15, Aoba walked around in the nearby city of Uji for three days, visiting locations that included the company's headquarters, the sources said.

Security camera footage also showed the suspect walking near sites featured in the studio's television anime series "Sound! Euphonium," a story about the music club of a high school in Uji, the sources said. Fans of the series often visit a bridge, an intersection and other relevant spots in the city.

The police searched Aoba's apartment in Saitama, near Tokyo, on Friday, confiscating items including Kyoto Animation products, according to the sources. They also found a smartphone in the apartment.

Aoba did not have a mobile phone when he was apprehended by the police in Kyoto right after the incident.

The police have obtained an arrest warrant for murder and are expected to officially serve it on Aoba when he recovers.