New Zealand’s summer of unrestricted movement and social interaction has been brought to an abrupt halt by three new community cases of COVID-19.

After an emergency cabinet meeting on Sunday, Prime Minister Jacinda Ardern placed largest city Auckland into a snap, three-day lockdown and reimposed social distancing requirements for the rest of the country while authorities race to find the source of the new infections. Genomic sequencing shows them to be the more virulent U.K. strain of the virus, the Ministry of Health said on Monday.

"This result reinforces the decision to take swift and robust action around the latest cases to detect and stamp out the possibility of any further transmission,” the ministry said.