They later said there were injuries and a man has been detained for questioning.
The shooting has left one person dead and three more injured, AFP reported citing the town's mayor.
A hospital said it's treating four people injured in the shooting but didn't know the extent of their injuries.
The San Diego Sheriff's office told The Daily Beast that one man was arrested in connection to the shooting and is being questioned by investigators.
San Diego County Sheriff's Office said incident took place at the Chabad of Poway house of worship sometime after 11.30am local time. "This is a developing situation".
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However, Huddersfield may relish a chance at one more mighty upset before they make their return to the Championship next season. That we are close is already rather surprising because previous year we were 25 points behind. "If we win it, we win it".
The Palomar Medical Center Poway received one patient from the synagogue and expected up to four wounded people in all.
ABC 10 notes, "The synagogue was hosting its Passover Holiday Celebration which was scheduled to begin at 11 a.m., according to an event announcement". Police are now preparing to raid his home, reports say. "We urge you to allow deputies to safely do their job", the following tweet read.
The Poway sheriff's department sent out a tweet saying the shooting occurred just before 11:30 a.m. Saturday.