The Police Minister's backing his officers for their use of the emergency mobile alert system in Christchurch

The alert was sent out about 8.30 last night, warning a 79-year-old woman with a medical condition -- believed to be dementia -- had gone missing from Bishopdale.

It sparked a major public search that found her within two hours.

Mark Mitchell praised the effort of Police.

He says Police try not to use the system too much as they want to be responsible in the way they use it... as they don't want to over use the feature as it would mean people would become desensitised to it.

But he says in this case, its use was absolutely justified and led to a great result.