Three members of a California family were killed yesterday after their rental car collided with a gasoline tanker truck between Kekaha and Waimea along Kaua'i's Kaumuali'i Highway, Kaua'i police said.

A fourth family member, an 8-year-old boy, was last night reportedly in critical condition at The Queen's Medical Center, police said.

Police have not released the names of the victims but said they were visitors.

Of the four accident victims, two were described as boys close in age, said Lt. Ale Quibilan, acting commander for the department's patrol services.

The accident occurred about 10:30 a.m. The family's mid-size rental car was reportedly on the shoulder of Kaumuali'i Highway facing west near mile marker 24 in Waimea when the driver apparently attempted to make a U-turn and was broadsided by a Gaspro truck that was heading west, police said.

The mother died at the scene and the father died at Kaua'i Veterans Memorial Hospital. One of the couple's two sons died while being transported via air ambulance to The Queen's Medical Center.

The Gaspro truck driver was treated at Kaua'i Veterans Memorial Hospital and released.

The three deaths raise the number of traffic fatalities on Kaua'i this year to 11, according to police.

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com and Peter Boylan at pboylan@honoluluadvertiser.com.