WA has recorded no new locally acquired cases overnight after extensive testing of the infected hotel security guards close contacts.

Genomic sequencing results has revealed the security guard has the highly contagious UK strain of the virus.

The mutant variant is thought to be up to 70 per cent more contagious.

Contact tracers are still examining the movements of the hotel quarantine worker, and 17 separate sites have been linked to the man over the past week.

66 close contacts have been established, 13 have tested negative and 11 high-risk contacts have been moved into hotel quarantine.

Premier Mark McGowan said WA Police will launch a full investigation into how the security guard became infected.

“This will run in parallel with the review led by the former Chief Health Officer,” he said,

“We will leave no stone unturned to ensure we find out exactly what happened to prevent it from happening again.”

More than 3000 tests were conducted yesterday, and clinics are expected to remain open until 10pm tonight.

Masks will continue to be mandatory until the end of the week and police are taking a “common sense” approach to mask enforcement.

Coles and Woolworths have been permitted to open from 7am, but the Premier said he was disappointed to see people panic buying from shops yesterday.

“I urge people to be reasonable and only take what you need,” he said.

Regional border checkpoints have been reinstated across the state, and the G2G Pass system will be reinstated later today.

Seven checkpoints have been set up across the Perth metropolitan area and eight in regional WA.

“If you are travelling between regions ensure you have supporting evidence,” the Premier said.

Meanwhile, FIFO workers will be unable to leave the Perth, Peel and South West regions until restrictions are lifted.

Non-essential retail shops have closed and an expansion of WA’s mandatory SafeWA system has been brought forward to 6am tomorrow.

Schools will remain closed this week, but childcare centres are open only to children of essential workers.

The lockdown across Perth, Peel and the South West regions is expected to finish at 6pm on Friday.

Click play to watch the full press conference.