PERTH, Australia — The Australian west coast city of Perth will lock down for three days after a returned traveler was apparently infected with the coronavirus while in hotel quarantine.

Western Australia state Premier Mark McGowan said on Friday masks will also become compulsory in the city of 2 million people for three days from midnight.

The cause of concern was a 54-year-old man who arrived in Perth on April 3 on a flight from China and went into mandatory 14-day hotel quarantine.

A couple from India on the same floor of the hotel were infected with a virus variant identified in that country as more contagious. The variant spread to a mother and daughter from Britain who shared a room across a corridor.

The man was released from quarantine on April 17 after testing negative but tested positive after flying to the east coast city of Melbourne on Wednesday. The test result was announced on Friday.

A friend he stayed with overnight in Perth tested positive for the coronavirus on Friday, becoming the first case of community transmission in Western Australia in more than a year.