Central Newfoundland's health authority is expanding its COVID-19 testing in Gander, N.L., following a school's shutting its doors Wednesday after someone connected with the school tested positive for COVID-19.

St. Paul's Intermediate said it had to close for "operational reasons," and posted a letter from Dr. Monika Dutt, Central Health's medical officer of health, to the school community on Twitter on Tuesday night, informing parents and guardians that someone associated with the school had been diagnosed with COVID-19.

A public health investigation, including contact tracing, is underway, the letter said. Dutt told CBC News on Wednesday the source of the case is not yet known.

"Right now, we're very much in early stages and doing our investigation," she said.

On Thursday, Central Health will begin offering COVID-19 testing to anyone in the town between the ages of 12 and 40, with or without symptoms, at the Steele Community Centre. Testing will take place from 10:30 a.m. to 6 p.m., with no appointment necessary.

The health authority said anyone recently who recently attended social gatherings or who has frequent interactions with the public be tested, but did not say whether the testing is connected to the St. Paul's case.

Dutt declined to give specifics on the school-related case, saying anyone considered at risk will be contacted directly.

Daniel O'Brien, assistant director of programs for the central and western offices with the Newfoundland and Labrador English School District, says any cases of COVID-19 connected to a school involve conversations with public health, and any staff members who have had contact with the case will need to isolate and get tested.

O'Brien said so many staff members at St. Paul's needed to isolate while awaiting testing that classes had to be suspended.

"At no point in this particular investigation with public health has there been any concern noted by them for the safe operation of our schools," he told CBC News on Wednesday afternoon.

"Even with St. Paul's today, we could have opened school under normal operations … but we felt it best given the timing and the information that we had at hand to make an operational decision to suspend classes."

O'Brien said the school is still open, and some staff were in the building Wednesday.

O'Brien said it's possible classes will be suspended for at least part of Thursday, depending on when teachers get their test results back. The district aims to open the school again as quickly as possible, he added.

At least one Gander parent was on edge Wednesday morning, and pushing for all schools in the town to close and move instruction online.

"I'm a bit afraid, I'm not going to lie," said Jennifer Humphries.

Humphries's three daughters were all at home Wednesday. Two attend St. Paul's, but her eldest goes to the town's high school, Gander Collegiate. Since students from St. Paul's and Gander Collegiate ride the same school bus — although they sit distanced from each other — Humphries said she wasn't taking any chances.

"I was very disappointed that all the schools were not closed today. That was a big disappointment with me," said Jennifer Humphries.

"I'm sure I'm not the only parent that feels that way today either," she told CBC News on Wednesday morning.

Neither Humphries nor her daughters had been contacted yet by public health, she said.

Dutt said she had "no qualms" about recommending schools stay open.

"School is important. And I would encourage people to keep their children at school if they feel they can," she said. "And if anything changes we would definitely recommend differently, if there was a risk seen."

According to Dean Ingram, president of the Newfoundland and Labrador Teachers' Association, the feelings of parents like Humphries show the importance of clear and transparent information from government and public health.

"We feel it's incumbent upon [government] to have clear information that not only demonstrates the extent of the cluster, but also what measures are being taken to ensure safety when students and our members, and those who work in schools, enter them."

Ingram said privacy should be respected, but a lack of information leads to rumours and increased anxiety among parents and teachers.

"Instead of giving generic statements about an individual under 20, what schools are affected?" he said.

"Because in the absence of information, that creates vacuums. Vacuums get filled, and when they get filled that leads to rumours that may or may not be founded."

Also in Gander, a COVID-19 testing clinic was set up from noon to 8 p.m. NT for employees of the town's Walmart, following a positive case identified at the store. According to the store, it was a contractor who was last on site Thursday.

Dutt said in that case, no workplace transmission or wider risk to shoppers has been seen so far, "but we are still gathering information."

While that clinic is only for Walmart employees, she urged anyone experiencing symptoms to be tested.

"We are finding recently that it's people who just didn't think they had COVID-19, but had symptoms, who got tested," she said.

As of Wednesday there were 53 active cases of COVID-19 in the province. One of Wednesday's three new cases was in the Central Health region, a person under 20 years old, and is under investigation.