Four people were injured in a five-vehicle accident on the H-1 Freeway near Kunia that wreaked havoc on yesterday's pau-hana traffic.

The accident occurred about 2:35 p.m. in the westbound lanes near the Kunia onramp to the freeway. Police said a tractor-trailer flipped on to its side, blocking all Wai'anae-bound lanes of the freeway. Four other vehicles were involved.

A mobile crane hoisted the truck upright and the freeway was re-opened at about 5:30 p.m.

The 46-year-old male driver of the truck was in serious but stable condition at The Queen's Medical Center, said Bryan Cheplic, spokesman for the city Department of Emergency Services.

A 23-year-old woman who was a passenger in one of the other vehicles also was in serious condition, he said. The woman's 1 1/2-year-old daughter was in the vehicle with her but escaped injury, he said.

A 44-year-old man and his 12-year-old son in another vehicle were taken to Pali Momi Medical Center in stable condition, Cheplic said.

The cause of the accident was under investigation. At one point, police reported that the freeway resembled a "parking lot" and the normally busy afternoon traffic was made even worse. Police closed the freeway's westbound lanes from Waikele.

Reach Curtis Lum at culum@honoluluadvertiser.com.