The police in San Diego rushed to a mosque Monday afternoon after reports of an active shooter, the authorities said.

Ahmed Shabaik, chairman of the mosque that was targeted, the Islamic Center of San Diego, wrote in an email that at least one person, a security guard, had been killed.

The authorities have not yet confirmed any deaths or injuries. The police department said the situation was “active but contained.”

Todd Gloria, the mayor, wrote on social media that he was “aware of the active shooter situation at the Islamic Center of San Diego,” and urged the public to avoid the area. He said the authorities would release more information as soon as it becomes available.

The center is the largest mosque in San Diego County, hosting daily prayers and regular seminars.

This is a developing story. Check back for updates.