"It's definitely him. We have tracked him from Iceland," Fernando Ugarte, part of the team monitoring the orca's progress, said by telephone Monday from a ship in the fjord.
Keiko is arguably the world's best-known whale, given his starring role in the three "Free Willy" films that were released in the 1990s, as well as a brief animated series shown on television.
Having spent most of his life in captivity, volunteers spent years training him for life in the wild. He was released from his pen in Iceland in July and swam nearly 870 miles to a western Norway fjord.
The orca surprised and delighted Norwegians, who petted and swam with him, and climbed on his back as he splashed in the Skaalvik Fjord, about 250 miles northwest of the capital, Oslo.
"He is completely tame, and he clearly wants company," said Arild Birger Neshaug, 35.
Neshaug said he was in a small rowboat with his 12-year-old daughter, Hanne, and some friends when they spotted Keiko on Sunday.
"We were afraid," Neshaug said. "But then he followed us to our cabin dock. At first we were skeptical, and then we tried petting his back. Finally the children went swimming with him."
He said the orca stayed by their dock all night and into the day on Monday, happily eating fish tossed to him by the families.
Newspapers expressed tongue-in-cheek surprise over the whale coming to Norway, since the oil-rich Scandinavian nation of 4.5 million people is the only country that commercially hunts whales despite a global whaling ban.
However, Norway's whalers only hunt minke whales.
Ugarte is monitoring the whale on behalf of the Ocean Futures Society and the Humane Society of the United States. He said Keiko was in excellent shape, but still seems to prefer humans to other whales.
Keiko, which means "Lucky One" in Japanese, was captured near Iceland in 1979 when he was two and spent most of his life in captivity in Canada and Mexico.
His appearance in the 1993 film "Free Willy" and later sequels helped spark a campaign to free him. He was rescued from a Mexico City amusement park in 1996 and rehabilitated at the Oregon Coast Aquarium in Newport, Ore., before he was airlifted back to Iceland in 1998 and taught to catch fish. Keiko's rehabilitation cost $20 million.
Ugarte said his team will continue monitoring Keiko's progress and movements.