The second confirmed case is a four-year-old boy from Tafuna who goes to the same school as the first confirmed measles case.
RNZ Pacific reports the Department of Health sent 39 samples to Hawaii for testing on Monday and 26 came back negative while one was positive for measles.
The samples are both nasal swabs and serum - the nasal swabs tested negative, but the serum samples have to be sent to a Centers for Disease Control and Prevention (CDC) lab as Hawaii didn't have the capability for serum testing.
Department of Health epidemiologist Scott Anesi said right now the Hawaii state Department of Health lab is not capable of doing serology on the serums.
"[This] is why we separate the tests between nasal-pharyngeal and serum. So the nasal-pharyngeals came back negative but the confirmatory for that is the serology.
"So that serum gets forwarded off to the CDC lab."
CDC is also testing for other viruses to include dengue.
As of Thursday there were 49 probable cases of measles.
The age range of the probable cases is two months to 13 years.
An eight-year-old girl was confirmed to have the disease on April 18.
Meanwhile, the number of vaccinations administered as of April 24 is 164.
However, the Health Department said some parents have refused to have their children vaccinated.
All territory schools closed on Monday and will remain shut until at least May 12.
A declaration of a public health emergency was issued by Governor Lemanu Peleti Mauga on Tuesday.
An investigation is underway by Health Officials in American Samoa to detect the source of a measles outbreak.
Health authorities have set up 17 vaccination sites as they work to determine the severity of the outbreak.
Clinics and church halls are being used as vaccination centres across all five of the US territory's inhabited islands.