British explorer Benedict Allen disappears during expedition to find tribe in Papua New Guinea

USA TODAY

Search efforts are underway to locate a British explorer who disappeared while searching for an elusive tribe in Papua New Guinea.

Writer and adventurer Benedict Allen, 57, was dropped off in a remote part of Papua New Guinea by a helicopter several weeks ago. Allen, who's appeared on BBC programs and written several books, was searching for members of the Yaifo tribe, according to the BBC.

Allen was supposed to be on a flight out of Papua New Guinea on Monday, but did not make the flight, his management company told NBC.

Allen's older sister, Katie Pestille, told BBC it was "out of character" for Allen to miss his flight.

"For everybody else, it's very exciting, all the expeditions and all the things he does, but for his sister and his wife, it's more of a worry," she told BBC.

In a September blog post on his website, Allen said he hoped to make contact with the Yaifo tribe, whom he first encountered 30 years ago.

"Last time ... the Yaifo "greeted" me with a terrifying show of strength, an energetic dance featuring their bows and arrows," Allen wrote. "On THIS occasion who knows if the Yaifo will do the same, or run off, or be wearing jeans and t-shirts traded eons ago from the old mission station."

He said that like his journey decades before, he planned on venturing into the wilderness with no satellite phone, GPS or companion.

"But of course I may not even (have) made it there, even aged 26 it was a very hard hike up through rather treacherous terrain," Allen said.

He noted that returning to his pickup location would not be easy, especially at his "advanced age."

"Either I must paddle down river for a week or so – or enlist the help of the Yaifo, as I did last time; together we managed to achieve the only recorded crossing of the Central Range," he said.

Shortly before his departure he tweeted that he was on his way to the airport, and jokingly said "don't try to rescue me, please."