(AP) - Police investigating a possible robbery at a Birmingham home early Sunday instead found five people dead inside, authorities said. Birmingham Police Sgt. Johnny Williams said officers arrived at the house around 3:30 a.m. He told reporters that investigators are interviewing potential witnesses but so far have made no arrests. "Someone out there knows more information," said Williams. We know someone is going to do the right thing. The victims' identities and the causes of death were not immediately released. Birmingham authorities launched a homicide investigation and police believe more than one person was involved. "It obviously appears to us this horrific crime was not a random act of violence," said Birmingham Police Chief A.C. Roper. The two-bedroom house, which is made partly of cinderblocks, was built along a busy street in west Birmingham. Vacant homes sit beside houses where some residents have lived for years. One is Beatrice Houston, who lives across the street from the home where the bodies were found. Houston, who is 64, said she believes a woman, her son and her brother had lived in the house for the last year or so. She said she didn't know the neighbors' names, but started worrying when she saw groups of young men hanging around the house at odd hours. Still, she said, her neighbors didn't cause many disturbances. "I never had any problem with them," she said. They were cordial. I just kept to myself. Doreatha Moss lived in the house, a white building with green trim now surrounded by police tape, until late 2010. She doesn't know who moved in to take her place. "I don't know anything about it now other than that there's all the time a bunch of young guys hanging around there," said Moss, who still returns to visit friends. That's not good. Houston said most of her neighbors are still in a "state of shock" "They never had any trouble over there," Houston said. Associated Press writer Greg Bluestein in Atlanta contributed to this report.