Three cases of measles are confirmed today in an outbreak of the disease in Waikato, the Waikato District Health Board (DHB) says.
Seven cases were suspected and more were likely, it said.
The outbreak appeared to have started about a week ago in Te Awamutu, Waipa, south of Hamilton and its surrounding communities, medical officer of health Dr Dell Hood said.
The DHB had written to parents of children attending schools or early education centres in the area advising them of the outbreak which involved students at Te Awamutu College.
"Because these cases have been in different places in the school holidays, it is very likely more cases will occur ... in other schools and preschools," Dr Hood said.