The bodies of two sailors killed in the annual Sydney to Hobart yacht race have been returned to shore, as the race continues in wild conditions.

A sailor aboard Flying Fish Arctos and one on Bowline were fatally struck by their respective boat's boom, a large horizontal pole at the bottom of the sail.

Both yachts have since retired from the race - two of the 17 pulled out by 8.45am on Friday after a west-southwesterly change brought strong winds to the southern NSW Coast and Bass Strait.

The deaths are the first in the race since 1998, when six sailors died in storms, triggering reforms to safety protocols.

Line honours favourite Master Lock Comanche is among the boats to have withdrawn from the race. (Dan Himbrechts/AAP PHOTOS)

Cruising Yacht Club of Australia vice commodore David Jacobs said the deaths would be investigated but many of the circumstances were still unknown.

"We always want to improve safety wherever we can, so we will do an investigation," he said.

"If there's something that boats can do to try and prevent this happening, we will implement it."

The identities of the two sailors have not been made public, but Mr Jacobs said several members of one boat were relatively new to the sport.

"But when you say they're an amateur crew, there are very specific safety requirements," he said.

Cruising Yacht Club Vice Commodore David Jacobs says the race will "absolutely" continue. (Mick Tsikas/AAP PHOTOS)

Mr Jacobs stressed the race would continue and the conditions were not extreme.

The fatality aboard Flying Fish Arctos occurred about 30nm east-southeast of Ulladulla on the NSW south coast late on Thursday night.

Crew members attempted CPR but could not revive their teammate, notifying the Australian Maritime Safety Authority about 11.50pm.

Flying Fish Arctos altered her course to arrive at Jervis Bay on Friday morning.

The crew member aboard Bowline was struck approximately 30nm northeast of Batemans Bay about 2am and fell unconscious, with CPR also unsuccessful. A police vessel escorted the boat to Batemans Bay.

Prime Minister Anthony Albanese paid tribute to the sailors who lost their lives.

"We have sadly awoken to tragedy in the Sydney to Hobart with the awful news two sailors have lost their lives," he said.

"Our thoughts are with the crews, their families and loved ones at this deeply sad time."

By Neve Brissenden in Sydney