It was imposed after the country's first cases of Covid-19 were detected in Fiji's second-largest city.
Health minister Ifereimi Waqainabete told a news conference on Wednesday the extension is necessary to prevent any further outbreak .
He said authorities will conduct intensive testing that will involve house visits and mobile testing stations.
"We know these restrictions have not been easy for many within the Lautoka confined area. But take comfort in knowing that these tough decisions we're making could very well spare us enormous future suffering," he said.
"No one wants to see a large scale outbreak of this virus in Fiji. That means making hard calls today that keep this virus at bay."
Dr Waqainabete said the public response to voluntary fever clinics has been disappointing.
A nationwide nighttime curfew also remains in place.
Fiji has five confirmed cases of Covid-19, a number that's remained unchanged since the 25th of March.