MOSCOW — A Russian icebreaker carrying over 100 tourists and scientists to see emperor penguins in Antarctica has been crunching through pack ice and should reach clear water soon, a shipping official said Wednesday.

The Captain Khlebnikov icebreaker has been struggling to free itself from heavy sea ice near Snow Hill Island in the Weddell Sea. It was supposed to return to Ushuaia, Argentina, two days ago but now is not expected until this weekend at the earliest.

Officials have said the people onboard weren't in any danger and were using the unplanned stop to take helicopter tours of the area. Snow Hill Island lies off the northern end of the Antarctic Peninsula, which juts up toward South America.

Tatyana Kulikova, a spokeswoman for the Fareastern Shipping Company, which owns the ship, said the icebreaker has broken through 5.5 kilometres of pack ice since Tuesday and is now less than one kilometre from clear water. She spoke Wednesday to the ITAR-Tass news agency.

The shipping company initially said the cruise ship was waiting for stronger winds to break up the huge ice pack, but Kulikova said the icebreaker was successfully freeing itself even though the winds remained light.

"The icebreaker keeps moving thanks to the skills of its captain and the crew," she said.

The cruise was advertised as a unique opportunity to watch emperor penguins in their natural habitat. Natalie Amos, a spokeswoman for Exodus Travel, said 51 British tourists were among the ship's 101 passengers.

Two-week Antarctic tours aboard the Captain Khlebnikov range from $13,890 (C9,350) to $22,690 (C15,280) per person. The Finnish-built icebreaker has been used as a cruise ship for several years and carries two helicopters.