Teachers at one of the country's largest second level schools have expressed concern at what they say are mixed messages they received from the HSE in relation to being deemed a close contact of a person with Covid-19.

St Oliver’s Community College in Drogheda closed to more than half its students after more than 30 of its teachers were alerted yesterday via the Covid tracker app that they were close contacts of a virus case.

They were advised to begin isolating immediately and to await a call from the HSE to arrange testing.

The alerts came after it was confirmed that a staff member at the school had contracted the virus.

However, while some teachers were tested this morning, others were told by the HSE that they did not have to isolate after all, or do a test, and were free to go about their business.

The school has been in discussions this evening with the Department of Education and the HSE to seek clarity on the situation.

The Department of Education has told RTÉ News that a full public health risk assessment was undertaken at St Oliver’s.

It said that following this assessment public health officials concluded that teachers contacted by the Covid tracker app were not close contacts.

In a statement, it said public health officials had reviewed data from the app along with the information gathered from the public health assessment carried out at the school, including an interview with the person who had contracted the virus, and an "assessment of overall compliance with control measures outlined in the national guidance for school setting; and reviewing the local infection prevention and control measures".

It said the school assessment was a "broad and more detailed assessment of the risk factors identified" and that this determined the actions that were required to be undertaken.

The department said that since the teachers who had been contacted by the Covid tracker app were not close contacts they did not need a test and should continue to attend school.

A teacher at St Oliver's told RTÉ News that staff there are shocked and confused by what has happened.

Responding to the explanation from the Department of Education, the teacher said the HSE had told her earlier today that the app had made "a mistake".

She queried whether the Covid tracker app could be regarded as accurate or not when it comes to teachers in schools.

"We are not very confident," she said.

The teacher, who is among those who received a close contact text alert, said: "We are all beside ourselves.

"It’s the shock of getting the alert and then being told it’s a mistake without any explanation as to what the mistake is. There is this idea that schools will stay open at any cost. We feel like cannon fodder."

Meanwhile, the HSE earlier said that the number of Covid-19 cases in schools is 131, with 96 cases believed to have arisen through community transmission, and another 35 where transmission may have occurred in a school.

To date, 96 schools have had to test students or teachers for the virus, with 2,100 tests carried out.

The breakdown of these tests between students and teachers is not yet known.

Speaking at a HSE briefing on Covid-19 this afternoon, HSE Chief Clinical Officer Dr Colm Henry said that cases in schools are not driving community transmission.

The HSE has said it cannot comment on individual cases or outbreaks to protect the privacy and confidentiality of those involved.

In a statement to RTÉ News, it said that when a case of Covid-19 is identified which is associated to an educational facility, public health professionals engage directly with the person, or family as appropriate, and asks them about their contacts.

It said responses and recommendations for each facility may well differ, depending on the circumstances identified by public health.

St Oliver's Community College caters to more than 1,200 students and has 120 teachers.