Two people were killed yesterday and two others were injured, one critically, in separate high-speed traffic accidents on the Big Island that happened within a half-hour of each other.

The fatalities were the eighth and ninth of the year, compared with four at this time a year ago, Big Island police said.

A 28-year-old Hilo man died in a head-on, two-vehicle collision at approximately 1:14 a.m. yesterday on Queen Ka'ahumanu Highway, 0.3 miles south of the 71-mile marker.

South Kohala patrol officers said the lone occupant was driving north in a 1989 Honda four-door sedan when he crossed the center line and collided with a 2010 Kia multi-purpose vehicle headed in the opposite direction on the two-lane state highway.

The Kia's driver, a 21-year-old Kailua, Kona woman, was pinned in the vehicle and was freed from the wreckage by Hawai'i County firefighters using extrication tools. She was taken by Fire Rescue personnel to North Hawaii Community Hospital, and later flown to The Queen's Medical Center in Honolulu, where she was listed in critical condition.

A 28-year-old man who was a passenger in the Kia was also taken to North Hawaii Community Hospital, where he was listed in serious condition.

The driver of the Honda was later removed by firefighters using special equipment and taken to Kona Community Hospital, where he was pronounced dead on arrival at 5:28 a.m. The man's identity was withheld pending notification of next of kin, police said.

Neither driver was wearing a seat belt, police said.

Traffic Enforcement Unit officers have started a negligent homicide investigation and have ordered an autopsy on the Honda driver.

Minutes earlier, at approximately 12:52 a.m., a 36-year-old man suffered life-threatening injuries when he lost control of his motorcycle and crashed on Honokohau Road in Kailua, Kona.

The man was identified as David K. Waipa of Waikoloa.

Kona patrol officers said Waipa was operating a 2001 Suzuki motorcycle and heading west when he struck the curb on the right side of the road and was thrown from the bike. Fire Rescue personnel took Waipa to Kona Community Hospital, where he died at 1:30 a.m.

Waipa was not wearing a helmet, police said. Authorities believe both speed and alcohol were factors in the crash.

Anyone with information regarding either of these accidents is asked to contact police at 808-961-8889.