Thousands of residents in a rural NSW town have been put on alert after Covid was detected in the sewage.

Fragments of the virus were found in the treatment plan at Bourke, in the state’s west and some 750km from Sydney.

NSW Health said the sample was taken on June 22 from a plant which serves about 2000 residents.

It is the first time the virus has been detected at this site.

“NSW Health is urging everyone in this area to be vigilant for the onset of any cold-like symptoms, and to get tested immediately and isolate if they appear,” the health department said.

Community members are urged to remain vigilant and get tested and the health department is working on increasing testing capacity for the region.

There are concerns the outbreak has spread outside of Sydney. Photo / NCA 

NSW recorded 11 new cases on Thursday including one mystery case.

Of the five new cases reported to 8pm, two are a woman and a man from Sydney’s southwest who are linked to the West Hoxton birthday party, which was attended by a person associated with the Bondi outbreak.

A teenager from Sydney’s eastern suburbs, who is linked to the Bondi cluster, and a woman in her 20s from Sydney’s eastern suburbs, who is a close contact of a previously reported case, were also included.

The six new cases after 8pm feature Agriculture Minister Adam Marshall, who attended the Christo’s Pizzeria in Paddington at the same time as a previously reported case linked to the Bondi cluster.

Three women, who are close contacts of a previously reported case who works as a hairdresser at a Double Bay hair salon, have also tested positive. All have been in isolation while infectious.

The source of the infection of the hairdresser, who lives in western Sydney, is under investigation.

A man in his 40s, who is linked to the West Hoxton birthday party, tested positive — meaning there are now 11 cases linked to the gathering.

Urgent investigations are underway to determine how another man aged in his 40s, who is not yet linked to a known case or cluster, caught the virus.

There have been 49 local virus cases since the limousine driver who transported aircrews between their hotel quarantine accommodation and Sydney airport returned a positive result.

This includes 36 linked to the Bondi cluster.

NSW Premier Gladys Berejiklian on Thursday described the outbreak as the “scariest period” NSW has gone through since the beginning of the pandemic.

More cases are expected to be announced later on today.