In an "astonishing" scene, members of an Austrian family terrorized by decades of incest and imprisonment met for the first time at a clinic where psychiatrists are helping them recover, authorities said Tuesday. Details of the emotional gathering emerged as police said DNA tests confirmed Josef Fritzl is the biological father of his daughter's six children. The retired electrician confessed Monday to imprisoning his daughter Elisabeth for 24 years in a warren of soundproofed cellar rooms, sexually abusing her, fathering seven children with her and discarding the body of an one, who died in infancy, in a furnace. Three of the children were locked in the underground labyrinth with their mother for years and had never met their other siblings or grandmother, who lived upstairs. Hospital officials said Elisabeth, five of the children and Fritzl's wife Rosemarie spent their first moments together Sunday. "It is astonishing how easy it worked that the children came together, and also it was astonishing how easy it happened that the grandmother and the mother came together," clinic director Berthold Kepplinger said. Now 42, Elisabeth was 18 when she was imprisoned in the secret annex her father built beneath his apartment in Amstetten, a working-class town 75 miles west of Vienna. Under the circumstances, she and the children were doing "quite well" in the care of a team of specialists, Kepplinger said. One of the children, a 19-year-old girl, was in critical condition and undergoing dialysis at another hospital, and was not part of the reunion, hospital officials said. Forensics experts carted boxes of belongings Tuesday out of the Fritzl home and investigators said they were combing through his other properties but had found no other hidden rooms. Fritzl, 73, led his wife to believe that Elisabeth had run away to join a religious cult when she disappeared and authorities said there was no evidence the suspect's wife knew what was going on or was involved. Franz Polzer, head of the Lower Austrian Bureau of Criminal Affairs, said Rosemarie's other children told authorities they noticed "absolutely" nothing about their father's double life. Fritzl faces up to 15 years in prison if convicted on rape charges, the most grave of his alleged offenses. However, prosecutors said Tuesday they were investigating whether he can be charged with "murder through failure to act" in connection with the infant's death, which is punishable by up to 20 years in prison. Fritzl's lawyer, Rudolf Mayer, said his client was under psychiatric care. Asked whether he showed any remorse, Mayer said: "I cannot say at this point." Fritzl "is really hit by this. He is very serious, but he is emotionally broken," Mayer told The Associated Press. However, prosecutor Gerhard Sedlacek said Fritzl was "calm, completely without emotion" when he was placed in pretrial detention Tuesday. Residents of Amstetten questioned how the abuse could go undetected for so long. Town authorities authorized the construction of a basement addition to the gray stone apartment building Fritzl owned and lived in, in 1978, city spokesman Hermann Gruber told the Austria Press Agency. He said inspectors examined the project in 1983 - the year before Elisabeth was imprisoned - and found nothing suspicious. Officials said three of the children - the hospitalized 19-year-old, and two boys, aged 18 and 5, - "never saw sunlight" until they were freed from the basement on Saturday. The other three children lived with Fritzl and his wife. The couple registered those children with authorities, saying they found them outside their home in 1993, 1994 and 1997, at least one with a note from Elisabeth saying she could not care for the child. Kepplinger said the 18-year-old could read and write in a "reduced form." He said Elisabeth has spoken "quite a lot" about what she went through in captivity, but he declined to provide details. "It was definitely dreadful for her and for her children," Kepplinger said. Leopold Etz, a regional police official, told the Austrian Press Agency that Fritzl apparently chose which children would live upstairs with him and his wife according to whether they were "crybabies." Etz said he could not confirm Austrian media reports that Fritzl took several "men's vacations" to Thailand with unidentified German friends in the 1990s. Fritzl was a dues-paying member of Amstetten's fishing club, and club official Reinhard Kern said "there was never a problem with him." "Whether he actually went fishing or not, how am I to know? Maybe it was an alibi," Kern said. The case started unfolding on April 19 when the imprisoned 19-year-old woman was found unconscious and was taken to a hospital. After receiving a tip, police picked up Elisabeth and her father on Saturday. Fritzl freed the captive children the same day, Polzer said. Amstetten Mayor Herbert Katzengrueber told the AP in an interview that Fritzl was personable and well-liked, and that the town had honored the suspect and his wife on their 50th wedding anniversary in 2006. Katzengrueber said he was at a loss to explain how such an atrocity could happen. "No one can really explain it," he said. "I am appalled and saddened that such a thing could happen in my hometown. ... These have been awful and sad days." About 200 people, many holding candles, gathered for a vigil in Amstetten's main square late Tuesday. In steady rain, they sang hymns and prayed for the victims. "This is tragic," said 19-year-old Jaqueline Vogel, as tears trickled down her face. Austria is still scandalized by a 2006 case involving Natascha Kampusch, who was kidnapped at age 10 and imprisoned in a basement outside Vienna for more than eight years. In an interview with Puls4 private television, Kampusch, now 20, expressed empathy for the Fritzl family's ordeal and offered to help them financially. But she also questioned the wisdom of moving the victims to a clinic for care. "Those are the surroundings that they are used to. Just to rip them out of there without a transition cannot be good," she said.