An essential worker visited a takeaway shop and three service stations, some multiple times, across the Riverina over a four-day period last week.

They later tested positive to COVID-19, prompting the Murrumbidgee Local Health District [MLHD] to declare the stations in West Wyalong, Hay and Tooleybuc potential exposure sites on Tuesday.

Further investigations have led to one of the West Wyalong exposure periods to be listed as a close contact.

Anyone who ate in the Coolabah Tree Cafe at the Coles Express service station on the Mid-Western Highway at Wyalong between 7pm and 7.45pm on Thursday, August 26 is now considered a close contact.

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They must get tested and isolate for 14 days regardless of the result.

People who checked into the cafe at the relevant times will be sent a text message from NSW Health with further information, and should expect a follow-up call. Anyone who was in the venue at the time and did not check in or hasn't heard from the NSW Health public health unit is asked to called the PHU on 1300 066 055.

Those who were at the cafe at a different time or did not eat a meal there is not considered a close contact and does not need to call the hotline, the MLHD said.

"We're encouraging anyone with the mildest of respiratory symptoms to please come forward and get tested," the MLHD's pandemic lead Emma Field said.

The previously-announced venues at Hay, Tooleybuc and Wyalong remain at casual contact status.

The venues of concern include:

The upgrade comes after a second detection of fragments of COVID-19 were found in sewage at Temora, following an initial discovery late last week.

"That [second positive sample] tells us something is going on in that Temora area," Ms Field said.

"As a result we are making sure our testing out there continues."

Mobile testing has been deployed to Hay, Tooleybuc and West Wyalong and appointments are not necessary.

Tests can be carried out at Toppy Hall in Neeld Street in West Wyalong between 10am and 3pm on Wednesday, Thursday and Friday this week.

In Hay, people can be tested at the hospital in Murray Street between noon and 4pm on Wednesday and Thursday.

Those wishing to be tested in Tooleybuc can attend the Bridge Keeper's Cottage in Murray Street between 10am and 2pm on Wednesday and Thursday.

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