TORONTO -- Tens of thousands of Ontario high school students were unable to take their first online literacy test Thursday because of widespread technical issues.

The Education Quality and Accountability Office pulled the plug on the "voluntary" online test for which most of the province's 900 secondary schools had signed up to participate.

Education Minister Mitzie Hunter expressed her disappointment in the cancellation of the online test, and said she expected the EQAO would try to quickly get to the bottom of the technical problems.

"I know the students wanted to write it today and were prepared to write it today," said Hunter. "It's unfortunate that the system did not support that completion of the test today."

The EQAO, which oversees standardized testing in schools, was conducting the first provincewide trial of its new online assessment program, but the students could not access the test.

Shortly after testing got underway, the EQAO posted a tweet saying the test was cancelled due to technical issues and apologized to participating schools and students for the failure.

"Further information will be provided to directors of education to help them communicate to their school communities shortly," said a note posted on the agency's website.

"We recognize all of the work that schools have done to prepare for this trial."

The voluntary test was meant to serve as a trial of the technical readiness of the EQAO and the schools to support online assessments, and a "risk-free" way for students to take it ahead of the next scheduled assessment in March 2017.

If students passed the online test, it would count, but if they failed or didn't complete it, they would be considered "first-time eligible" for the test next spring.

The program was open to all 72 school boards, as well as First Nations and private schools, but the EQAO did not immediately respond to a request asking exactly how many students and schools had signed up to participate.