The Daily Breeze reports ( http://bit.ly/139MLNa) the samples were taken from the Machado Lake area between Wilmington and Harbor City.
It's the first instance of West Nile in LA County this year.
The virus also has been found in samples taken from Fresno and Tulare counties.
Mark Hall, operations supervisor for the Greater Los Angeles County Vector Control District, says officials would begin strategizing about what can be done to educate and protect LA residents.
He said signs would be posted around Harbor Regional Park to alert people that the virus had been found there.
West Nile is passed through the bite of an infected mosquito. Mosquitoes become infected by feeding on infected birds.
Information from: Daily Breeze, http://www.dailybreeze.com