(CNN) -- One week after 11-year-old Celina Cass was last seen, her body was found Monday by divers searching the Connecticut River, New Hampshire Senior Assistant Attorney General Jane Young said.
"We have brought Celina home, not the way we wanted to bring her home," Young said early Monday evening.
The girl's father, Adam Laro, said he was heartbroken and grasping for answers after hearing the news.
"I ... can't believe what's gone on," Laro told HLN's "Nancy Grace" show on Monday night. "I have no fingers to point ... I hope there will be some answers, that's what I'm asking."
Young said that the case -- which had been considered a "missing persons" case -- is now being investigated as a "suspicious death." No one has been arrested or named publicly as a suspect in what is now a criminal investigation.
"Based on what we have seen visually, we are treating it as suspicious," the official said.
Celina's body was found around 10:30 a.m. Monday by divers from the New Hampshire Fish and Game Department near a hydroelectric plant outside West Stewartstown, New Hampshire, according to the attorney general's office.
Young described it as a "routine search because of the proximity to (Celina's) home," about one-quarter mile away. The site is also near the Canadian border, where the Connecticut River forms the border between New Hampshire and Vermont.
The discovery came a day after Laro -- who was in the hospital when Celina went missing -- said that he was like others "wondering where my daughter is" and hoping she was safe.
On Monday night, the father thanked all those authorities and residents who had put their time and effort into finding Celina.
He said his memories of his daughter are "beautiful, beautiful, just a wonderful hearted person."
"(She was) someone who was loving and caring to a lot of people," Laro said. "That's how I would like to remember her."
Celina was last seen in her room, at her computer, around 9 p.m. July 25, according to police. CNN affiliate WMUR reported that her parents told authorities the girl was gone when they went to wake her up Tuesday morning.
Since then, local, state and federal investigators had searched for her and for clues about her whereabouts "by air, by land, by water," Young said Sunday evening.
Young said on Monday that authorities, including FBI agents, had received nearly 500 tips prior to finding the girl's body.
She described investigators' focus Monday around Celina's home as "routine," after being asked about yellow crime tape there and the removal of a vehicle. The aim is to "determine if we have any evidence" in places around where the girl was last seen alive.
Young added that the discovery of the girl's body should help authorities "hone the investigation, so you will (still) see searches conducted in different areas."
An autopsy will be conducted on Celina's body on Tuesday morning in Concord, New Hampshire, said Young. The medical examiner will work to determine the cause of the girl's death.
Celina's father said that he had not spoken with his ex-wife, who lived in the house with the girl's stepfather of about a year, since the girl went missing. He described his ex-wife as a "great mother," and added he had positive interaction with the stepfather.
"(It was) a household that supposedly gave her great love, that's what she always told me," Laro said.
CNN's Chuck Johnston contributed to this report.