TUCSON, Ariz. - Health officials in Arizona say the largest current measles outbreak in the United States is in part because some workers at a federal immigration detention center refuse to get vaccinated.

Pinal County Health Department leaders say detention staff are responsible for 9 of the 22 cases in Arizona.

In Casa Grande, a total of eight cases have been reported -- the most in any one area.

The people 12 News spoke with there are well aware of the outbreak and were upset to learn about the employees not being vaccinated.

"They don't do anything until there's a huge outbreak and then they react," said Marsha Tucci, who lives in Casa Grande.

Officials say the employees are passing it to each other and then going out into the community.

MORE: Pinal health officials: ICE not cooperative during measles outbreak

Authorities have confirmed 22 measles cases in Arizona since late May. They all stem from the Eloy Detention Center, an Immigration and Customs Enforcement facility managed by the Corrections Corporation of America.

"If they're in contact with people from out of the country that are not being vaccinated, they should," said Joanna Strong, who lives in Mesa, where one case has been reported.

Pinal County health director Thomas Schryer says the outbreak likely began with a migrant but that detainees have since been vaccinated.

MEASLES EXPOSURE AREAS: Arizona Department of Health Services

Schryer said ICE employees at the large facility have not been as cooperative. Nine of the 22 total cases were facility staff.

"Our soldiers have to be vaccinated. So [ICE employees] should be vaccinated too," Strong said.

ICE says the agency is working closely with health officials to monitor detainees and employees. CCA says most of its workers have gotten immunized or are wearing surgical masks while looking for proof of immunity.