VICTORIA -- The Royal Canadian Navy will launch an inquiry into how a sailor went overboard and was lost at sea off the coast of California while his ship was returning home from deployment this week.

The search for Master Sailor Duane Earle concluded around 5:30 p.m. Tuesday after searchers spent upwards of 30 hours scouring the waters 500 nautical miles west of San Francisco.

Commodore Angus Topshee, the commander of Canadian Fleet Pacific, thanked the United States military and coast guard Wednesday for their assistance in the search and said officials are still baffled by how Earle went overboard.

"We really cannot explain how he came to be in the water," Topshee said. "We will be conducting a board of inquiry to determine how that happened."

The 47-year-old sailor and father was last seen aboard HMCS Winnipeg around 5 a.m. Monday and was declared missing when he failed to attend a meeting that afternoon.

Topshee said the ship’s upper decks are surrounded by guardrails and are off-limits to crewmembers overnight.

"No one should be on the upper decks at night," the Pacific fleet commander said from Canadian Forces Base Esquimalt. "You can only get off the ship via the upper decks."

Maritime Forces Pacific spokesperson Lt.-Cmdr. Tony Wright clarified Wednesday that "night" would include the early morning hours before the sun comes up.

Topshee added that crewmembers on the ship’s decks are expected to wear a chemically activated light in case they go overboard.

The search involved several aircraft, including the Winnipeg’s embarked CH-148 Cyclone helicopter, which flew approximately 22 sorties during the search effort, Topshee said.

Weather conditions at the time of Earle’s disappearance hindered the search.

"Winds were high, there was some precipitation and the seas were four to five metres," he said. "It is harder than finding a needle in a haystack."

Topshee said the loss of the sailor brings an “unimaginably difficult time for the family and the crew,” especially as the sailors were eagerly anticipating a happy return home to CFB Esquimalt for the holidays.

"His family is currently in the grieving process as a result of this tragic loss," Topshee said, adding the crew is  struggling to deal with the "horrible and completely unexpected tragedy."

The navy will now conduct a board of inquiry to determine what led to Earle’s disappearance over the side of the ship.

"A board of inquiry does take a period of time to conclude," Topshee said. "We will learn what we can from it."

Prime Minister Justin Trudeau issued condolences to Earle’s family and shipmates Wednesday.

"For over 30 years, MS Earle selflessly answered the call of duty," Trudeau said in a statement. "His dedication to our country and its values represented the very best of what it means to be Canadian."

HMCS Winnipeg was initially due back in Esquimalt on Dec. 17, but its return will be delayed by the search.