People wait in line at a COVID assessment centre at Women's College Hospital during the COVID-19 pandemic in Toronto on Wednesday, September 23, 2020. THE CANADIAN PRESS/Nathan Denette

Multiple COVID-19 assessment centres in Ontario are reporting no test availabilities on Tuesday and at least one network of hospitals in the Toronto area is reporting technical difficulties due to high demand.

Tuesday marked the first day of the transition to appointment-only COVID-19 tests at Ontario’s 153 assessment centres. Walk-in services were all suspended on Sunday in order to give the province’s lab network a chance to catch up on their backlog of nearly 80,000 tests and to allow time to prepare for the new system.

The new rules were announced last week amid reports of six-hour wait times, with lines to get a COVID-19 test often wrapping around the assessment centres.

On the day that assessment centres reopened, the Scarborough Health Network (SHN) tweeted that their booking website had crashed.

“Due to the high volume of visitors on our website to book an appointment for COVID-19 testing, we are currently experiencing technical difficulties. We apologize for the inconvenience and are working to resolve it.”

The health network had closed pre-registration for test appointments on Monday after receiving 1,700 requests. Their website said that they would reopen on Tuesday at 9 a.m.

As of 10:30 a.m., the pre-registration form at SHN was available, but appeared freeze halfway through the process.

Due to the high volume of visitors on our website to book an appointment for #COVID19 testing, we are currently experiencing technical difficulties. We apologize for the inconvenience and are working to resolve it.

— Scarborough Health Network (@SHNcares) October 6, 2020

Other assessment centres have also been slammed with test requests. In East York, Michael Garron Hospital’s booking website says that there are “no appointments to be booked online” for those who are experiencing symptoms of COVID-19.

“Continue to self-isolate and check back tomorrow for an appointment or go to your nearest emergency department if your symptoms worsen,” the website says.

The same message is seen for the hospital’s “pediatric and family COVID-19 test” category.

The Unity Health Network, which encompasses assessment centres at St. Joseph’s hospital and St. Michael’s Hospital in downtown Toronto, has no appointments available until at least Friday.

Those trying to book an appointment for Friday get the following message:

“We apologize. There are no available appointments at the moment. We encourage you to check back regularly as spots will be released as they become open. A new block of appointments will be released at 7 p.m. each day. We apologize for the inconvenience.”

Mount Sinai is using the ticketing website Eventbrite to book appointments. Their website indicates they are “sold out.”

There are also no appointments available at North York General and Sunnybrook Hospital is completely booked until Thursday.

Ontario experienced a record backlog of COVID-19 tests last week, nearing 90,000 tests still under investigation. Ontario Premier Doug Ford said the backlog was due to a technician shortage.

On Tuesday, the province confirmed that some of the tests have been sent to the United States for processing.

More than 55,000 COVID-19 tests are under investigation.