LONDON — In 2017, Jolie King and Mark Firkin hit the road in a white Toyota Land Cruiser, beginning a journey that over the next two years would take them from their home in Perth, Australia, across large stretches of Asia as they meandered toward Europe.

Photos and videos posted on social media accounts documenting their adventure show the pair swimming in the turquoise waters of Bali, trekking to Everest base camp and driving through the valleys of Pakistan surrounded by snow-capped peaks.

Then, at the end of June, their posts suddenly stopped.

On Thursday, officials confirmed that the couple were among three Australian citizens detained in Iran for the past 10 weeks. Rights groups have expressed concerns that they may have been tortured, and a fellow prisoner’s husband reported that Ms. King had been held for weeks in solitary confinement.

It is unclear why the pair were detained, and the Iranian authorities have not responded to requests for comment about Ms. King and Mr. Firkin. Pouria Zeraati, a prominent Iranian journalist, said the pair had been detained after flying a drone near Tehran without a permit.