(CNN) -- Five people were found dead Sunday at a home in Birmingham, Alabama, by officers responding to a report of a robbery in progress, police said.
The bodies were discovered about 3:30 a.m. (4:30 a.m. ET), Birmingham police said in a statement. Authorities have initiated a homicide investigation.
"We don't think it's random at this point," said Sgt. Johnny Williams, citing evidence collected at the scene. He declined to specify what was found.
Williams added that police believe there may have been more than suspect involved, but so far no arrests have been made.
No further details were immediately available. The victims' identities were being withheld pending notification of relatives.
"Our detectives are out working this case as we speak," said Williams.
CNN's Georgette Knuckles contributed to this report.