South Australian police have seized mobile devices from the pizza bar worker whose lie sent the state into a hard lockdown.

Officers from Task Force Protect are examining the devices as part of their investigation into the circumstances of the Parafield coronavirus cluster, Police Commissioner Grant Stevens said on Sunday.

The cluster includes several cases linked to the Woodville Pizza Bar, including one man who told contact tracers he ordered a pizza from the shop when in fact he worked there.

Cafes, restaurants and other hospitality and retail venues that closed for two days due to the scare reopened on Sunday.

Just one week after the first case in the Parafield cluster was reported, more than 4500 people directly linked to it were now in quarantine, SA chief public health officer Nicola Spurrier said on Sunday.

They include 21 close contacts linked to the Woodville Pizza Bar, including staff and many of their family members.

They had all been tested, but not all the results were known at this stage, she said.

Four people linked to the Woodville Pizza Bar were admitted to a medi-hotel on Saturday night, Professor Spurrier added.

As of Sunday, there were 37 active cases in the state.

The man worked at the Woodville Pizza Bar as well as the Stamford Plaza medi-hotel. Photo: ABC

Contact tracing ‘on steroids’

South Australians are being urged get tested at the first sign of any coronavirus symptoms. Almost 17,000 tests were conducted on Saturday.

Professor Spurrier said the current level of work being done to trace everyone linked to the Parafield cluster was like “contact tracing on steroids”.

Text messages are still being sent out to people, including customers of the Woodville Pizza Bar, urging them to go into quarantine until someone from SA Health contacts them.

“Please follow those instructions because this is a pretty critical time for us in South Australia to make sure that we’re locking all of those end parts of these chains down,” Professor Spurrier said.

There were no new cases reported after a third round of testing at Anglicare’s aged care facility at Brompton, the location Professor Spurrier described as the “most vulnerable” setting.

• See a full list of SA coronavirus hotspots and alerts here

Police issue hundreds of cautions and fines

Meanwhile, SA Police says its officers issued hundreds of cautions and fines to South Australians over alleged breaches of COVID-19 restrictions during the state’s brief lockdown and in the hours after.

Police cautioned people and businesses 337 times from when the stay-at-home order came into effect at 12:01am on Thursday until seven hours after it ended on Sunday morning. Police issued 157 fines during the same period.

An SA Police spokesperson stressed that fines were only handed out to people who “blatantly disregarded the requirements of the directions, while the greater population of South Australians were amazing and did the right thing”.

“We implore the South Australian community to continue to do the right thing as police and numerous other departments across the state continue their efforts against COVID-19,” an SA Police statement said.

-ABC