San Diego County health officials say six more children may have caught measles at a doctor's office where another infected child was treated.
Four other children are already known to have caught the virus in the county's first outbreak in 17 years.
The outbreak began last month when a child contracted measles during a family trip to Switzerland. The child returned to San Diego and infected two siblings.
More than 50 children at a charter school, a swim school and a day care center attended by some of the infected children are being quarantined as a precaution.
