At least nine people confirmed to have highly infectious measles visited Disneyland parks in Southern California last month, health officials said Wednesday.

The California Department of Public Health confirmed seven cases of measles in the state, and two others in Utah. Three more California residents are also suspected to have measles, but those cases are not confirmed.

The nine confirmed to have measles said they visited Disneyland and/or Disney California Adventure Park in Orange County between Dec. 15 and Dec. 20, 2014. The source of the infection is still under investigation, but health officials said it's likely that a person with measles was at one of the theme parks during that time period.

A spokeswoman for Disneyland told NBC4 Thursday that it is safe to visit the park. The only dates in which visitors were at risk are Dec. 15 to 20, according to the spokeswoman.

"We are working with the health department to provide any information and assistance we can," said Dr. Pamela Hymel, chief medical officer at Walt Disney Parks and Resorts.

A Disneyland spokesperson said further questions will be directed to the Department of Public Health.

The Borbons of San Jose visited the theme park during the infection window. No one in the family is showing any symptoms. The family also said all of their vaccinations are up to date.

"You don't ever want to get a virus," Kristine Borbons said. "It's a little scary, but I don't think it's to a hysterical point."

The confirmed cases in California live in Alameda, Orange, Riverside and San Diego counties and in Pasadena. They range in age from 8 months to 21 years.

Six of the seven California cases were not vaccinated for measles, including two who were too young to be vaccinated, officials said. One had been vaccinated with two doses of the MMR vaccine.

Both Utah cases were not vaccinated, a Utah Department of Health spokeswoman said.

People can be infectious with measles for nine days. Measles typically begins with fever, cough, runny nose and red eyes and within a few days a red rash appears, usually first on the face and then spreads downward to the rest of the body. Measles is a highly infectious, airborne disease.

Measles has been eliminated in the United States since 2000, but outbreaks have occurred in Western Europe, Pakistan, Vietnam and the Philippines, health officials said. Disneyland and other theme parks are international attractions with visitors from all over the world, including areas where measles is an epidemic.

More information about measles can be found on the California Department of Public Health website.

NBC Bay Area's Jean Elle contributed to this report.