Photo: Twitter - Glacier National Park

Fires in Glacier National Park have blocked a route for several hikers.

A wildfire has cut off the return route for dozens of people staying in a Glacier National Park backcountry chalet, leaving them the choice of remaining until rangers tell them it's safe or hiking out along a longer and more difficult trail, park officials said Friday.

Park rangers also planned to lead out 39 other hikers who were staying in backcountry campsites near fires that broke out after a passing lightning storm on Thursday, Glacier spokeswoman Lauren Alley said.

It's peak tourist season at the Montana park, and the stone chalet built more than a century ago is a top attraction in one of the busiest parts of Glacier. There are typically between 40 and 50 guests and 10 staff members at the chalet each night, with most visitors arriving by foot or horse along a steep trail nearly 11 kilometres from Lake McDonald Lodge on the park's main roadway.

A lightning strike ignited a fire in the forest somewhere between the lodge and the chalet. Neither structure is threatened, but park officials determined that it was unsafe for those at the chalet to return by the same trail Friday.

Thirty-nine of the 42 guests staying at the Sperry Chalet decided to hike out and three stayed behind, said Suzie Menke, the office manager of Belton Chalets Inc., which runs the chalet.

They must take a rugged trail more than 21 kilometres long that crosses two mountain passes and can take eight to 10 hours to walk. That trail ends up on the eastern side of the park, on the other side of the Continental Divide from Lake McDonald Lodge.

For those who stay, the chalet has running water, a full-service kitchen and 17 private rooms — but it doesn't have electricity and only spotty cellphone coverage.