Five crew members of a Matson Navigation Co. container ship were injured when their vessel encountered "extreme sea conditions" this week en route to Honolulu.

All five were taken to The Queen's Medical Center yesterday morning after the ship arrived at Honolulu Harbor, but their conditions and names were not being released, said Gary North, senior vice president for Matson's Pacific operations.

None of their injuries was life-threatening, North said.

The SS Matsonia was midway between Long Beach, Calif., and Honolulu on Monday when it encountered 15- to 20-foot swells, North said.

"Sea conditions between Hawai'i and the Mainland have been very rough during the past week due to unusually strong winter storm systems, which have moved through this part of the Pacific," North said. "The seamen were injured while attempting to secure a store-room hatch, which had sprung open by heavy seas."

U.S. Coast Guard officials in Honolulu received a distress call from the ship about 10:15 p.m. Monday, said Chief Petty Officer Marsha Delaney.

The injuries included broken bones, cuts, bumps and bruises, Delaney said.

The Matsonia was too far from Honolulu — about 1,100 miles away — for a helicopter flight, she said. The nearest potential help was a cruise ship 500 miles behind the Matsonia.

Turning the Matsonia around to meet the cruise ship could have put the vessel in bad weather, Delaney said.

Instead, a C-130 aircraft made a nighttime drop Wednesday of medical supplies needed to keep the patients comfortable.

Coast Guard officials are investigating the cause of the accident and injuries, Delaney said.

Reach Mike Gordon at mgordon@honoluluadvertiser.com.