On Oct. 11, Benedict Allen tweeted a couple of lines that now seem ominous: "Marching off to Heathrow. I may be some time (don't try to rescue me, please - where I'm going in PNG you won't ever find me you know...)." The British explorer's family says the 57-year-old has gone missing in Papua New Guinea, where he planned to make contact with the Yaifo, described by the Guardian as one of the world's few isolated tribes, and one Allen had first encountered three decades ago.
"No outsider has made the journey to visit them since the rather perilous journey I made as a young man," he wrote in his blog.
He had planned to be back in Port Moresby, the capital, by Sunday in order to make his flight to Hong Kong, where he had a speaking engagement.
The BBC reports a pilot who dropped Allen off at a remote location weeks ago is tracking his route, and the police have been engaged.
The BBC quotes Allen, who chose to travel without modern devices like GPS or satellite phone, as saying he wasn't quite sure how he'd get out of the jungle: "Either I must paddle down river for a week or so—or enlist the help of the Yaifo, as I did last time." Allen's sister calls the situation "ghastly," but the BBC sounds an optimistic note, describing the reality of traveling in the country "hugely unpredictable and normal schedules don't apply," meaning it's quite possible he got waylaid by weather.
It adds, "Knowing Benedict, it is also quite possible that he has accepted an invitation to stay on longer for a tribal ceremony—it can also be considered an insult to refuse." (This woman tweeted something eerie before being killed on her Amazon trek.)
This article originally appeared on Newser: Family Says Explorer in Search of Lost Tribe Has Gone Missing