The father arrested on suspicion of setting fire to his house in southwestern Japan has told police that he "had worries at the workplace," investigative sources said Wednesday.

Police have learned that Kenichiro Suemune, a 40-year-old lieutenant in the Maritime Self-Defense Force, who allegedly started a fire at his house in Kitsuki, Oita Prefecture,at around midnight on Sunday, had been seeing a doctor of psychosomatics until recently. Investigators are now looking into his relationship with coworkers.

Meanwhile, four bodies found in the house were confirmed to be of his four children aged between 5 and 14. His wife and three other children of the couple escaped the fire, some of them with injuries, while another child was not at home.

The four children who died are Suemune's eldest daughter Yukari, 14, the fourth son Masahiro, 9, the second daughter Mayumi, 7, and the fifth son Shigeru, 5. All of them were burned to death, according to the police.

Suemune told the police he poured oil in the house and set it ablaze because his wife did not see him off when he was leaving for Hiroshima, where he lives by himself due to his assignment as an MSDF officer, the sources said.

On weekends, he returned to Kitsuki from Etajima in Hiroshima, where he belongs to a maintenance unit for unmanned jets.