The Ministry of Health says there are two positive Covid-19 cases in Christchurch from the same household.

Covid-19 Response Minister Chris Hipkins says the case has been in Christchurch for up to a week.

One member of the household had recently returned to Christchurch from Auckland.

The case tested negative for Covid-19 before travelling to Christchurch, and got a second test once they became symptomatic, Hipkins said.

Hipkins said he cannot rule out a snap lockdown in Christchurch, but they are still waiting on more information before making that call.

The ministry says the local public health unit is identifying close contacts and exposure events, including any locations of interest.

A public health risk assessment is being done this morning and there will be an update after that.