Children from nearby schools were seen being evacuated as officers established a perimeter around the area, the outlet reported.
Mayor Todd Gloria said on X that he was aware of the situation at the Islamic Center of San Diego.
"I am aware of the active shooter situation at the Islamic Center of San Diego in Clairemont and am continuing to receive updates from law enforcement," he wrote on X. "Emergency personnel are on scene and actively working to protect the community and secure the area."
In another post, Gloria wrote, "Please avoid the area and follow instructions from public safety officials. We will share updates as more information becomes available."
California Gov. Gavin Newsom’s press office said the governor has been briefed on the "evolving situation" at the Islamic Center.
"The Governor’s Office of Emergency Services (@Cal_OES) is coordinating with local law enforcement," Newsom’s team wrote on X. "We are grateful to the first responders on the scene working to protect the community and urge everyone to follow guidance from local authorities."
The Islamic Center of San Diego describes itself on its website as the largest mosque in San Diego County.
The mosque shares an address with the Lower Campus of Bright Horizon Academy, a private Muslim school serving pre-K through 12th grade students, according to the school’s 2025 annual report.
Bright Horizon Academy reported enrollment of just over 350 students across its campuses. It was not immediately clear which grade levels are housed at the Lower Campus adjacent to the mosque, though the school’s high school operates at a separate location.
This is a developing story. Check back for updates.