Confirmed cases in Matamata come after a St Patrick's Day gathering at The Redoubt Bar and Eatery on March 17.

A cluster of confirmed Covid-19 cases in Matamata is linked to a St Patrick's Day celebration at a local bar, the Waikato District Health Board has announced.

There are now 23 confirmed cases in the Matamata area with most having attended the event at Redoubt Bar and Eatery on March 17 or linked to those who attended, the DHB said in a statement on Monday.

Work to date identifies the original case is linked to overseas travel, DHB Incident Controller for the health response in Waikato Leena Singh said.

CHRISTEL YARDLEY/STUFF The Redoubt Bar and Eatery closed its doors on Monday, March 23.

"The public health team continues to work through the connections of those affected to ensure we continue to link our positive cases and discount true community transfer.

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"With the Alert Level 4 lockdown now in effect, residents of Matamata can be assured that they are already undertaking the safest possible practice by isolating and should continue to follow the national guidance - to ensure they limit any further transmission people should avoid travel, wash their hands and practice social distancing.

CHRISTEL YARDLEY/STUFF A Covid-19 assessment centre has been set up at the Matamata-Piako Civic & Memorial Centre.

"Please stay in your bubble as this is the most effective way to eliminate the virus."

A new community-based assessment clinic is being set up on Monday at Matamata Civic Centre at 11 Tainui St and will be operating from 3pm.

Swabs taken from Matamata will undergo priority testing. Singh said any Matamata residents with symptoms of COVID-19 should contact Healthline or their GP and visit a Community Based Assessment Centre (CBAC).

CHRISTEL YARDLEY/STUFF Swabs taken from the Matamata testing station will undergo priority testing.

They should inform the staff if they had attended the Redoubt Bar during the previous two weeks, or if they had close contact with anyone who had. Any visitors to the town who had visited the bar on 17 March for the St Patrick's Day celebration who are experiencing symptoms should also follow these steps.

Singh said it was important to know whether there has been spread beyond Matamata.

Matamata-Piako Mayor Ash Tanner said while the rising number of cases is alarming, people should stay calm and listen to the advice given by the Ministry of Health.

CHRISTEL YARDLEY/STUFF Matamata now has a Covid-19 assessment clinic which opened on Monday.

"The number of increasing Covid-19 cases in Matamata is saddening and my sympathies go out to the families and businesses most affected by this."

He said in times like this people often "point fingers and lay the blame on others", but the community should be focused on making sure they are following all necessary guidelines.

"It's one of those things where people often think they are bullet proof, but no-one really is," he said.

"It's more important than ever that people follow the recommendations of the Ministry of Health and stay at home, otherwise more cases will show up and the lockdown will be extended, which is something none of us want. "