Benedict Allen, a British explorer who traveled to a remote jungle in Papua New Guinea to search for a lost tribe of headhunters for a BBC documentary, is feared to have gone missing. The family of the 57-year-old raised concerns Tuesday about his well-being after Allen did not arrive in Hong Kong where he was due to talk to the Royal Geographical Society.

Allen was dropped off by a helicopter in the jungle in the northwestern part of the country known as the Central Range three weeks ago and has not been heard from since. The father of three had no phone or GPS service. He was expected back in Papua New Guinea's capital Port Moresby on Sunday for a flight to Hong Kong.

In his last tweet on Oct. 11, Allen wrote that no one can get in touch with him as he is headed for the journey. He shared a cryptic message saying "don't try to rescue me, please."

Allen said in a blog post in October that in case people find his website and Twitter account silent, then they should not worry as he is “due back mid-Nov- it’s because I am still out there somewhere.” He said that "just like the good old days" he would not be taking a satellite phone, GPS or a traveling companion.

Allen's agent Joanna Sarsby told the Daily Mail: "His wife Lenka has not heard from him. She is very worried. He would never miss something like the Hong Kong talk unless something had happened."

"He is a highly experienced explorer, very clever and resourceful and adept at surviving in the most hostile places on Earth, and he would never give up. He may not be a young man anymore but he is very fit," Sarsby said. "He was trying to reach the Yaifo people, a very remote and reclusive tribe – possibly headhunters, quite a scary bunch. Goodness knows what has happened."

"I just imagine he might have been taken ill or is lying injured somewhere, perhaps with a broken leg, and maybe being helped by locals," she added.

Allen, who has made six documentaries for the BBC and has also survived a trek across the Brazilian rainforest in 1982 by eating his own dog,  lives in Bristol with his Czech-born wife and their three kids Natalya, 10, Freddie, 7, and Beatrice, 2. He appeared in a documentary filmed in Papua New Guinea - an island just north of Australia that is almost entirely made up of the thick jungle earlier this year.

In his last blog post in September, Allen said he had made the "first outside contact" with the Yaifo tribe 30 years ago and was returning "to create a brief record of their lives, if possible tracking down some of those... who'd remember me."

"No outsider has made the journey to visit them since the rather perilous journey I made as a young man three decades ago," he wrote on his website. "This would make them the remotest people in Papua New Guinea, and one of the last people on the entire planet who are out of contact with our interconnected world."

A Foreign Office spokesman said: “Our staff are assisting the family of a British man who has been reported missing in Papua New Guinea, and are contacting the local authorities.”