A man detained on suspicion of attempted murder died Thursday of injuries received in a car accident that occurred a day earlier while he was being transported in a police van, Saga Prefectural Police said.

According to investigators, the police van swerved into the opposite lane while traveling down a hill where it collided head-on with a truck at around 2:20 p.m. on Wednesday.

Yoichi Kawakami, 66, from the city of Karatsu, Saga Prefecture, was arrested in June over the alleged stabbing of a relative, according to the Saga Shimbun. He died in hospital Thursday morning.

Five people were injured in the accident, including Kawakami.

The accident occurred on National Route 203 in the city of Ogi. Black skid marks were found at the scene of the accident.

The van was on its way from a prefectural police office in Karatsu to the Saga District Public Prosecutor's Office.

Kazuhisa Iwasaki, a 47-year-old prefectural police official from the city of Karatsu who was driving the van, broke a femur in the accident, while Hirofumi Hirayama, a 49-year-old transport company truck driver who lives in Imari, injured both his legs.

Investigators plan to send papers to prosecutors on Iwasaki on charges of negligent driving resulting in death and injury.

Yoshiaki Makise, an officer working with the Saga Prefectural Police, said Thursday it is "highly regrettable" that an accident involving a police car killed the suspect.