There's been no trace of Bjørn Kenneth Amundsen, age 36, since he walked out of the national prison at Ila, west of Oslo, on an approved, short-term leave of absence last Thursday. He never returned.

Such prison leaves are common in Norway, where penal policies stress efforts to reintegrate criminals into society. Prison authorities have admitted, however, that they made a mistake in believing Amundsen would respect the liberty he was accorded.

Amundsen was in the second year of a 12-year prison term for multiple armed robberies, drug possession and car theft when he disappeared.

He previously has lived in Brazil and may already be on his way to South America, for all the Norwegian authorities know. "We don't even know if he has a passport, but we clearly fear he has left the country," said Stig Oma of the Asker og Bærum Police District.

Police have received about 10 tips from the public since releasing Amundsen's photo, but they haven't produced any concrete leads.

Warrants also have been issued with Interpol for the arrest of Amundsen, who's described as slender with blond hair and about 178 centimeters tall.