The family of a woman missing and believed dead in the Canterbury earthquake has suffered another cruel blow - her home was burgled while her children waited for news.

Producer and presenter Donna Manning is among the Canterbury Television (CTV) staff missing and feared dead after the regional television channel's building collapsed in Tuesday's 6.3 magnitude earthquake.

Her niece, Lisa Gardiner, said that while Ms Manning's two children were down near the collapsed building site Wednesday, thieves broke into their family home.

The home had been damaged in the quake and the family had been unable to shut and lock the doors. There was also no power or water at the house.

Ms Manning's children arrived to find property had been taken from inside the house.

They seemed to be holding up well despite this latest blow, Miss Gardiner said.

"It's just so sad," Miss Gardiner said.

"I find it unbelievable that people would do that."

The burglary raises concerns about how many properties are being targeted by thieves as people flee damaged homes or leave the city to escape the ongoing aftershocks.

On Wednesday night, six people were arrested for looting around the central city.

Superintendent Dave Cliff said there would be a 6.30pm curfew inside the central business district, and only those involved in the rescue effort would be allowed in.

"That's also about keeping out the criminal element, who we know will try and take advantage," he said.

Others have been profiting from peoples' desperation.

One man said someone went to buy a 750ml bottle of water in a Christchurch dairy but was asked to pay $10 for it.

There were other reports via Twitter - some other dairies were selling 2 litres of milk for $7.50 and service stations were charging $3 a litre for fuel.