According to preliminary information, the shooting happened near Linwood and Hartford avenues.
The female officer was shot in the thigh and was transported in stable condition to LAC+USC Medical Center, police said. Her injuries were believed to be non-life threatening.
Police said it was not yet known who ambushed the officer, but at least one person was in custody and a gun was recovered. Authorities said the incident was not an officer-involved shooting.
A search was underway for other possible suspects in the incident.
As the search continued with a massive police presence, 6th street was partially blocked off near the 110 Freeway, and 7th Street was blocked off between Bixel and Alvarado streets.