Photo/IllutrationThe Fukuoka prefectural police headquarters in Fukuoka (Asahi Shimbun file photo)

FUKUOKA—A husband and wife have been arrested on suspicion of firing an air gun in November last year at their 1-year-old son, who died the following month of a lung infection.

Masanori Jokei, a construction worker, and his unemployed wife, Ai, both 24 and living in Tagawa in Fukuoka Prefecture, denied the abuse allegation, according to Fukuoka prefectural police.

They were arrested Nov. 6.

Police are investigating the circumstances leading up to the infant's death, including whether he was systematically abused, as his body was covered in bruises likely from the assault.

The parents said they do not know how the bruises got there and that they never fired a gun at Yuiga, who died of the disease.

Police believe they shot dozens of plastic BB pellets at him with a rifle-shaped air gun, leading to injuries all over his body that would take three weeks to heal.

Ai called the 119 emergency number at 4:15 a.m. on Dec. 1, saying that Yuiga was not breathing. En route to a hospital, he was in a state of cardiac arrest and was pronounced dead at around 6 a.m.

At the time, Ai said: "He started to cry while he was sleeping and his breathing became shallow. His heart then stopped beating."

However, many welts were found on his body.

Jokei has claimed that his 3-year-old son fired the air gun. During the police investigation into the incident, several air guns were confiscated from the home.

According to the Tagawa child welfare center, a suspected abuse case involving the couple's eldest son was reported to them in January last year, as his cheeks were swollen. Ai, however, claimed that he had bumped into a wall. As the center judged that the parents had not caused the injury, they did not take the child into temporary custody.

At the time of the air gun incident, the couple was living with the 3-year-old eldest son, the third son, Yuiga, and their first daughter. The second son died of a disease.

The center is taking the eldest son, first daughter and second daughter, born in July, into protective custody.