A 6-month-old infant died Thursday night and six adults were injured after the passenger van they were riding in crashed in Kau, Hawaii County police said.

Police said the boy’s father, a 36-year-old man, was driving a 2011 Dodge van south on Hawaii Belt Road when it veered off the shoulder at about 5 p.m. in Kapapala.The driver and two other passengers, a 37-year-old man and 39-year-old woman, were treated and released from Kau Hospital.

The 6-month-old baby, identified as Yuta Suzuki, his 28-year-old mother, and two other passengers, a 30-year-old woman and another woman,  went to the Hilo Medical Center, where the baby was pronounced dead at 7:55 p.m. The boy’s mother was released. The two passengers are reported in serious condition.

Police said the adults were wearing seat belts, but the infant was not in a car seat.

Bystanders were performing CPR on the infant, when emergency personnel arrived on scene.

All seven in the van were Japanese nationals visiting from Shinonawata, Japan.

Police have opened a negligent homicide investigation.