"The police believe the case is characterised by a clear, planned deception," he said. "The basis for suspecting Tom Hagen has been gradually strengthened."
Investigators last summer announced that they now believed that Anne-Elisabeth Falkevik Hagen had been murdered, with the perpetrator or perpetrators faking evidence to make her disappearance seem economically motivated.
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Tom Hagen was ranked last year as Norway's 164th richest man with a fortune of 1.9bn kroner ($301m), although he had kept a low profile ahead of his wife's disappearance, leaving him unknown outside business circles.
According to Norway's VG newspaper, police seized the 70-year-old as he left his house to drive to his nearby offices at 8.30am yesterday morning.
Police cars stopped traffic in both directions and waved down Hagen's vehicle. After being arrested, he left in a police car, leaving his own abandoned on the road.
Svein Holden, one of the two lawyers who prosecuted Norwegian mass murderer Anders Behring Breivik, has been appointed to defend Hagen.
Police lawyer Åse Eriksson warned at the press conference that the investigation focusing on Tom Hagen still had a long way to go.
"We are still very early in the new phase of the investigation aimed at Tom Hagen, and it is especially important for the police to uncover Tom Hagen's role in the case and to find Anne-Elisabeth Hagen," she said, according to Norwegian state broadcaster NRK.
She said police had yet to clarify if any others are believed to be involved. For the first few months, the investigation was kept secret, with the suspected kidnapping only made public in January last year.
In March, Hagen said he believed the perpetrators must have been based locally and may even have been from among his acquaintances, as they had seemed to have known their way around his property.