Fritzl told captives he would gas them if they tried to flee

AUSTRIA: AUSTRIAN POLICE said yesterday that Josef Fritzl threatened to gas his daughter and children if they tried to escape from their prison underneath his house.

Fritzl (73) went to extraordinary lengths to keep his double life secret, police said, even pretending to be his daughter, Elisabeth, in a phone call to his wife in 1994.

Investigators are combing the 60m2 secret cellar Fritzl built under his house in Amstetten, west of Vienna, for evidence of the gas threat.

"It may have just been an empty threat to intimidate the captive woman and her children into not trying to overpower him," said Mr Helmut Greiner, a spokesman for Austria's federal investigators.

Elisabeth Fritzl was 18 when she vanished in August 1984. Her father locked her in a windowless secret cellar but claimed she had run away to join a cult.

In 1994 he made a brief telephone call pretending to be his daughter, asking his own wife Rosemarie to take care of the baby left days earlier on the doorstep.

The call corresponded to a note Fritzl had forced his captive daughter to write. He had left the note with the baby, Monika, one of seven babies fathered by Fritzl and the first of three he took from the cellar to raise with his wife.

"Rosemarie Fritzl reported it [ the call] to Amstetten police station in 1994 and the report was passed on to the prosecutors' office," said regional police official Reinhard Nosofsky.

"She could not explain the call and had not recorded it. We now know it was Fritzl."

Police insist that Rosemarie Fritzl had no knowledge of her husband's double life or the whereabouts of her daughter. "She had no reason to search the house or to think she [ Elisabeth] was in the cellar," said Mr Nosofsky.

Nearly a week after the 24-year mystery was solved, the first members of the Fritzl family have spoken to the media.

Josef Fritzl's sister-in-law Christine (56) told the Österreich tabloid that the retired engineer often spent entire nights in the cellar that was strictly off limits to everyone but him.

"He [ Josef] would go to the cellar every morning at nine and he would often even spend the night there," she said. "Allegedly it was to work on blueprints for machines he was selling. She [ Rosemarie] was not even allowed to bring him a cup of coffee."

Police insisted yesterday that they had no proof that Fritzl had an accomplice. Questions arose when video footage surfaced of him on a three-week holiday. Investigators say the captives were able to stay alive thanks to tinned food. Asked how Fritzl mounted the 300kg door to the cellar, police suggested the frame was hung before being filled with concrete.

Medical staff at Amstetten clinic where the Fritzl family are being treated have told how every day holds new wonder and terror for the Fritzl children.

Stephan (18) was so excited he kept trying to touch the air with his hands. The sun filled him with amazement, a trip in a lift with terror. Felix (5) is fascinated by everything from cows to mobile phones. "The world outside is so pretty," he told one doctor.

Extra security guards have been assigned to the Amstetten clinic after photographers began climbing nearby trees to try and get the first shot of the Fritzls.

In Vienna, former hostage Natascha Kampusch has said she was "deeply affected" by the fate of the Fritzls, two years after she escaped her imprisonment.

"I realised there were parallels to my own fate," she said to Germany's NTV news channel. She urged the family to take their time before talking to the media. "They need a lot of silence."

Meanwhile, Austrian chancellor Alfred Gusenbauer has attacked international media coverage of the Amstetten case.

"We will not allow Austria, our entire population, to be taken hostage by one criminal, appalling perpetrator acting alone," said Mr Gusenbauer to a crowd of 100,000 taking part in a May Day rally at Vienna's town hall.

"We will defend the reputation of our country, dear friends."