Two Melbourne aged care facilities have been forced into lockdown after residents returned positive tests for coronavirus yesterday.

A resident at dementia centre HammondCare in Caulfield tested positive to the virus on Monday but has since returned a negative result this morning.

The centre will remain in lockdown as a precaution while further testing is completed.

Staff also undertook coronavirus testing yesterday, which is set to continue at the facility today.

HammondCare senior nurse Angela Raguz told 3AW the case was under investigation.

"We have treated it as positive and have put in place all of our outbreak management plans," she told Neil Mitchell.

"We are now investigating and the Department of Health is investigating.

"We need to keep in lockdown."

Lynden Aged Care in Camberwell also informed families yesterday that a resident had been diagnosed with COVID-19, prompting the facility to close its doors to the public.

The aged care home is conducting testing and contact tracing of residents and employees today.

Source: 9News