French adventurer Jean-Jacques Savin, who set off in a rowboat from Portugal on Jan. 1 to cross the Atlantic solo, has vanished at sea with his boat found overturned and empty near the Azores archipelago, Portugal's navy said.

The 75-year-old Savin's support team had said in a Facebook post on Saturday that his body had been found inside the cabin of his sleek, purpose-built boat Audacious, but late on Sunday issued another statement signed by his daughter Manon that the body had not been recovered.

"To date we have no official confirmation from the Portuguese maritime authorities," she wrote.

A Portuguese Navy statement on Sunday said a search for Savin's boat began after a distress signal sent just before midnight on Thursday. The search involved a naval corvette, three aircraft and several merchant ships, one of which found a waterproof bag with Savin's documents inside, it said.

They located the boat capsized in turbulent seas and managed to lift it onto the naval ship on Saturday.

The search was called off after that, with an advisory issued to ships in the area alerting them to the possibility of finding the shipwrecked adventurer.

"There have been no further sightings or information since," a navy spokeswoman said on Monday.

Savin celebrated his 75th birthday at sea on Jan. 14.

On Jan. 19, he posted about problems with the solar charger of his water desalinator, but said he was "not in danger", as he was heading towards the mid-Atlantic port of Ponta Delgada in the Azores with fair wind.

"There's a beautiful marina with an airport next door. If I want to fix it (charger) I will have everything I need in place," he wrote then. "My goal is to go as far as I can each day as long as the wind is with me!"

In 2019, Savin crossed the Atlantic in a barrel-shaped capsule, from Spain's Canary Islands to the Caribbean. (Reuters)

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