Hunter New England Health announced 11 new cases in the 24 hours to 8pm Tuesday night.

Five were from Lake Macquarie, three from Port Stephens, two from Newcastle and one from Dungog.

A spokeswoman for MACH Energy, which owns the Mt Pleasant coal mine, confirmed that the man was working with a contractor on the site's rail loop project."

We have been keeping them very separate to our mining operation," she said.

People who work on the rail loop were sent home for testing, and his test came back positive about 6pm on Tuesday night, she said, while the site continues to follow protocols detailed in its COVID-19 response plan which includes contact tracing and deep cleaning in and around the Rail Loop Construction area.

"All other operational activities, including mining, processing and train loading, continue as normal," she said.

Hunter New England said its public health unit was working with Mach Energy, and that a risk assessment was underway to determine exposure to employees who were at the same time as the worker.

HNE Health is working with Medtech Services and Muswellbrook Shire Council to establish a drive-through testing clinic at Muswellbrook Showground, to support increased rates of testing. It is understood that may be up and running as quickly as Thursday morning.

In its daily update, Hunter New England said testing rates in the Hunter Valley had fallen and it urged anyone in the area with "even the mildest COVID-19 symptoms" to get tested and isolate while they wait for their result.

Last week, Centennial Coal said one of its workers at the Mandalong had tested positive and sent home workers for testing. The Herald understands that the worker later returned a negative test.

Deputy Premier John Barilaro was asked about COVID protocols at mines in Wednesday's regional press conference and admitted he had concerns.

"We should look at who's moving and where ... if it is because of a movement into a mine site outside of their LGA residence that is starting to worry me a little and I am happy to look into that a bit more," he said..

"The onus is on the mine operator - up to this point I have been very comfortable with it but perhaps there's more that needs to be done."