Two offshore energy rigs, threatened by a heaving field of metre-thick ice northeast of Sable Island, were expected to be evacuated by mid-afternoon on Monday.
As helicopters airlifted about 100 people from the platforms, which are 290 kilometres southeast of Halifax, a small fleet of vessels was dispatched to cut through the floes approaching the area.
The move was described as precautionary because the 25-kilometre long stretch of sea ice could damage the legs of both rigs.
Officials with ExxonMobil, owner of the Venture natural gas production platform, and Canadian Superior, operator of the Rowan Gorilla V exploration drill rig, said the facilities would be left empty until the ice leaves the area.
Michael Coolen, a vice-president of Canadian Superior, said the company will airlift all 75 staff from the Rowan Gorilla, but added he doesn't believe the jack-up rig is in danger of being knocked over.
"I wouldn't expect any damage due to the ice," he said.
However, the company suspended its Mariner natural gas exploration program, lifted its drill from the ocean and secured the well with concrete plugs.
It also dispatched seven vessels to break up any ice that threatens the rig's enormous steel legs.
The fleet includes the Terry Fox, a Canadian Coast Guard icebreaker, and six offshore tugs.
Mr. Coolen said some of the vessels will use their rear propellers to create small waves that will push the ice around the rigs. They will also use a water cannon to push the ice away.
Alan Jeffers, spokesman for ExxonMobil, said his company doesn't expect the ice will damage the Venture platform, which had a crew of 23 people aboard.
The Venture platform is the northernmost of the project's four facilities, which also includes the North Triumph, Thebaud and Alma platforms.
Mr. Jeffers said large ice packs in the area are rare.
"When they were doing the design work for the project they envisioned this happening once in every 50 years . . . The design is for worse (ice) than this."
The evacuation means Canadian Superior, a Calgary-based junior exploration company, will face delays and added expenses in its drilling program for natural gas.
"That's part of the exploration business," said Mr. Coolen. "It's quite a high-priced, costly business. In addition, we have various insurances we'll be notifying and hopefully that will help a bit there, too."
A Canadian Superior news release predicted it could be seven days before operations return to normal.
A spokesman at the Canadian Coast Guard centre in Dartmouth, N.S., said the ice was over a metre thick and was being pushed toward Sable by strong northerly winds.
It was expected to arrive near the island at about midnight local time on Monday night.