A group of high school students in Tasmania may have been exposed to several blood borne viruses after a teacher decided to use the same needle while taking blood samples.

The teacher was attempting to test the PH levels of their blood during a class experiment, but the science teacher did not sterilize the needles correctly, The Mercury reported.

As a result, 18 kids may have been exposed to viruses such as HIV and hepatitis B or C, according to the report.

"The risk of transmission is extremely low in this age group, but it is always a risk to share needles," Dr. Roscoe Taylor, the director of public health said. "This is an incident that should not have happened."

An education official said while the risk of students becoming infected is low – he is still demanding a full investigation.

“It is important that all students who took part in the testing undergo blood tests," Lin Thorp, the education minister, said.

Click here to read more from The Mercury.