New York State canceled 20,000 COVID-19 vaccine appointments on Thursday after a scheduling link was prematurely leaked to the general public.

According to state officials, the bookings involved the state-run site at Stony Brook University Hospital on Long Island. The website was not supposed to be live until Friday, according to Melisa DeRosa, a top aide to Governor Andrew Cuomo.

“The hypothesis is either it was hacked, or there was someone who leaked the link,” DeRosa told reporters at a briefing Friday morning.

An attorney for the State’s Office of Information Technology Services said clinics in Binghamton, Buffalo, Plattsburgh, Potsdam, and Utica were also affected, leading to cancellations. A spokesperson for the health department said the state suspended appointments for an additional 2,400 people at those sites. The incident has been referred to New York State’s inspector general for investigation.

“Two appointments at Stony Brook for my senior parents canceled,” one person tweeted on Thursday night. “Really continuing to look out for our vulnerable seniors, it seems. Way to go.”

Asked about the issue during the briefing, Governor Andrew Cuomo responded by saying “It’s not the first time it happened, right? There’s been similar cases,” a reference to the crowds that converged on the Brooklyn Army Terminal in Sunset Park on Thursday. In that case, word spread on social media that the city was administering extra vaccines on a first-come, first-serve basis. A spokesperson for Stony Brook University Hospital referred our questions to the New York State Health Department.

“[The state] has sole responsibility and authority for determining vaccine eligibility...and when appointments at the location will be made available on the State site,” the Stony Brook spokesperson said.

New Yorkers have also criticized the state’s vaccination website as confusing and glitchy.

DeRosa said the increased eligibility in recent days had caused a massive increase in web traffic, “causing the servers to go down.”

“We understand the frustration if someone got the link not knowing that there was devious intent behind how it got out,” she said. “However, there are seven million people vying for 250,000 shots, and the system has got to be fair.”

This story has been updated with additional data from New York State.