Oakland, California, police continued their search Thursday for at least one gunman involved in a shooting at a high school campus in which six adults were wounded, including two with life-threatening injuries.

Though the focus is on one gunman, it’s possible “there may be other individuals involved,” Oakland Assistant Police Chief Darren Allison said during a news briefing. Police have few leads about the shooter and a gun was not found at the scene.

Investigators are asking for the public’s help in identifying the suspect or suspects involved. Officials said they may hold a news conference Thursday afternoon to provide updates on the investigation.

The shooting was reported shortly before 1 p.m. Wednesday at the Rudsdale High School portion of the King Estate campus in the 8200 block of Fontaine Street, Allison said.

The campus houses four schools, ranging from middle to high schools, including the Bay Area Technology School, a public charter school for grades 6-12, and the Sojourner Truth Independent Study school, which operates an online learning program for K-12 students.

Police responded to the scene and found six adults, who have “some affiliation with the school,” suffering from gunshot wounds, according to Allison, who didn’t specify whether shots were fired inside or outside the school but said that some of the victims had been found inside the school.

The two with the most serious injuries were reported critical but stable at Oakland’s Highland Hospital on Wednesday while a third victim was stable, according to Alameda Health System officials. The others had non-life-threatening injuries.

Allison said Wednesday that at last check, one victim had been released from the hospital and two others were awaiting release. Police have not specified whether any of the victims were adult students or staff members at the school.

In a letter to families in the district Thursday morning, Oakland Unified Acting Superintendent Sondra Aguilera confirmed that Rudsdale, Sojourner Truth and BayTech are closed Thursday. Behavioral health staff will be available to provide psychological and emotional support to students and staff once they return to school.

“Our thoughts are with the people who were injured and their families, and we are hoping for quick recoveries for all of them,” Aguilera said in the letter. “We know how traumatizing this incident is for students, families, and staff alike.”

No students from Sojourner Truth were on campus Wednesday because of its virtual setup, said district spokesperson John Sasaki, who didn’t specify whether staff members were at the building.

The Oakland Academy of Knowledge, an elementary school, is also near the campus, but Sasaki said the shooting didn’t have any connection to the school.

Los Angeles Times staff writers Grace Toohey and Christian Martinez contributed to this report.