Police in Baltimore said that two people had died and 28 others were injured in a mass shooting early on Sunday morning at a housing block in the city.

The city’s police department said three of the injured were in critical condition after the incident at the 800 block of Gretna Avenue in the Brooklyn neighborhood of Baltimore soon after midnight.

An 18-year-old female was pronounced dead at the scene and a 20-year-old male was pronounced dead after being taken to a local hospital, the police said.

Nine people were transported from the scene to local hospitals, while 20 others affected walked into hospitals in the area, police said.

MedStar Harbor Hospital’s emergency department treated 19 patients on Sunday morning, all suffering varying degrees of injury from gunshot wounds after the incident, it told Reuters in an emailed response.

“Nine critically injured patients were stabilized and transferred to Baltimore trauma centers,” the facility said, adding that all but one patient had been released.

The police department said that at about 12:35am on Sunday, officers responded to calls of a reported shooting at the 800 block of Gretna Court.

Hundreds of people were gathered in the area for an event called “Brooklyn Day,” a witness told TV station Fox 45, adding that they had heard 20 to 30 shots fired.

CNN quoted Baltimore Police Acting Commissioner Richard Worley as saying there was as yet no information on suspects or a motive, but investigators were “working an extensive crime scene.”