(CNN) -- Authorities believe at least one person not in custody may have information about the deaths of eight people in a Georgia mobile home, Glynn County Police Chief Matt Doering said Sunday.
"I'm confident to say that there's somebody, at least an individual, that we would like to know about that's not at the scene," whether or not they were directly involved in the case, Doering said.
Seven people were found dead Saturday at a residence in the New Hope mobile home park in Brunswick, Georgia. Two others were hospitalized in critical condition, and one of them died Sunday, authorities said.
Police have "no known suspects," Doering told reporters Sunday afternoon. "We are not looking for any known suspects. That doesn't say that there are no suspects. They're just not known to us."
One person, 22-year-old Guy Heinze Jr., was arrested Saturday night, Doering said. Heinze is related to one of the victims, he said, and was the one who called 911. He told police he discovered the bodies when he arrived home.
Heinze was being held on suspicion of having a controlled substance and marijuana, as well as evidence tampering and making false statements to a police officer, Doering said. He told reporters Heinze has been cooperative.
"We're still looking for anybody and everybody that may be related to this," he said. "That naturally includes (Heinze). Of course we're looking at him." He stopped short, however, of calling Heinze a suspect in the deaths.
Autopsies on the victims were taking place Sunday in Savannah, Georgia, Doering said. Police have tentative identifications for the victims, who ranged from children to adults in their mid-40s, he said.
Police have been called to the home before, Doering said, but would not say why.
Doering remained tight-lipped Sunday about many aspects of the case, refusing to say how the victims died or to give a breakdown of male and female victims. All nine victims lived in the mobile home, he said, and police do not believe any of them conducted the assault.
He said police are making progress, and have narrowed down the timeline for when the deaths occurred.
Brunswick is about 300 miles southeast of Atlanta, on the Georgia coast.
Volunteers conducted an extended search of the area around the mobile home, but nothing was found, Doering said.
Meanwhile, police removed additional evidence from the mobile home. Authorities are examining surveillance video from nearby areas, but are not aware of any surveillance system in the mobile home park, he said.
"There is cause for concern," Doering said. "... We just simply don't have a whole lot to go on, and I'm not going to sit there and tell everybody not to be cautious, because people need to be."