Police Chief Scott Thurmond said at a news conference that police are still sifting through tips. Five of the injured victims remain in the hospital, he said.
The FBI is offering a $50,000 reward, and Crime Stoppers is offering $50,000, officials said. Tipsters can remain anonymous, they said.
Authorities have still made no arrests after Saturday's shooting killed four people and left 17 others injured in what police described as a targeted "hit" by multiple shooters who opened fire outside a popular nightspot in Birmingham's Five Points South district.
"This mass shooting has a heavy toll of the community as a whole, but nothing more harmful than the emotional and physical pain of these actual victims," Mayor Randall Woodfin said Monday. "But I want to make myself very clear on what the priority is: It is to hunt down, capture, arrest and convict the people who are responsible for this mass shooting."
The shooting rocked an area of restaurants and bars that is often bustling on weekend nights. The mass shooting, one of several this year in the city, unnerved residents and left officials at home and beyond pleading for help to both solve the crime and address the issue of mass shootings.
The shooting occurred on the sidewalk and street outside Hush Lounge, where blood stains were still visible on the sidewalk Sunday morning.
Thurmond has said authorities believe the shooting targeted one of the people who was killed, possibly in a murder-for-hire. A vehicle pulled up and "multiple shooters" got out and began firing, then fled, he said.
"We believe that there was a 'hit,' if you will, on that particular person," Thurmond said earlier.
Police said about 100 shell casings were recovered. Thurmond said that law enforcement was working to determine what weapons were used, but that they believe some of the gunfire was "fully automatic." Investigators also were trying to determine whether anyone fired back, creating crossfire.
In a statement late Sunday, police said the shooters are believed to have used "machine gun conversion devices" that make semiautomatic weapons fire more rapidly.
Officers found two men and a woman on a sidewalk with gunshot wounds, and they were pronounced dead there. An additional male gunshot victim was pronounced dead at a hospital, according to police.
Police identified the three victims found on the sidewalk as Anitra Holloman, 21, of the Birmingham suburb of Bessemer, Tahj Booker, 27, of Birmingham, and Carlos McCain, 27, of Birmingham. The fourth victim was pending identification.
