A school on the NSW Central Coast has closed after being informed of a possible COVID-19 case in a senior student.

The Green Point Christian College student will have additional tests on Friday.

“A senior student from our school will have further tests and the results will be known tomorrow afternoon,” school principal Phillip Nash said in a statement.

“Further communication will be issued this afternoon to advise if they have tested positive for COVID-19

“The school will be non-operational for the on-site attendance of staff and students today as an extra precaution while we await confirmation of the result.”

NSW Health Minister Brad Hazzard on Thursday also warned health authorities will be screening people at airports and transport hubs across NSW to ensure Melbourne residents from COVID-19 outbreak hot spots are not entering the state, and cars with Victorian number plates may be stopped.

Any who do try to enter NSW could face six months’ imprisonment or a fine of $11,000.

Mr Hazzard also revealed a woman this week caught the train from Melbourne to Sydney despite having respiratory symptoms and waiting on COVID-19 test results, labelling her behaviour “as silly as it gets”.

Tweet from @BradHazzard

Meanwhile, NSW health authorities are urging people in a Sydney suburb to be alert for COVID-19 symptoms after a local Woolworths worker tested positive for the virus.

The man had been in hotel quarantine in Victoria from June 11 to June 26 after flying from Bangladesh and tested positive to COVID-19 on the fourth day of his quarantine period.

He then flew from Melbourne on June 26 and returned to work at the supermarket in Balmain on June 27, with his employer noticing he had minor symptoms.

“The level of virus detected is very, very low … but because he’s also got symptoms, we’re just treating this as the utmost of precaution that he may be infectious,” NSW Chief Health Officer Dr Kerry Chant said on Thursday.

He worked at the store on June 27 and 28, and 50 employees are now in isolation after being identified as close contacts, with the store undergoing a deep clean.

Dr Chant said the man was assessed as non-infectious and cleared of the virus before he was discharged from Melbourne quarantine, but it’s unclear if this assessment included another COVID-19 test.

Mr Hazzard said anyone who visited the Woolworths store on either of the two days should come forward and be tested if they have respiratory symptoms.

Health authorities are also contacting people who sat around the man on Jetstar Flight JQ510 from Melbourne to Sydney on June 26.

Inner West Mayor Darcy Byrne admitted Balmain residents were feeling anxious.

“If they have been in the store, make sure that they go get a test straight away if there are any symptoms at all,” Mr Byrne told 2GB radio on Friday.

The state’s confirmed COVID-19 cases stand at 3211 from more than 870,000 tests, with one patient currently in intensive care in NSW.

-with AAP