A gas explosion in Christchurch destroyed a laundromat and put two in hospital.

An explosion at a Christchurch laundromat threw debris up to 20 metres and resulted in two people inside at the time being hospitalised.

The force of the explosion was powerful enough to shake nearby houses, according to reports on social media.

Fire and Emergency New Zealand (Fenz) was called to reports of a gas leak at the laundromat on Buckleys Rd, Linwood, about 6.40am on Monday.

IAIN MCGREGOR/STUFF Fire and Emergency NZ received a report of a gas leak in the building. Two minutes later, it exploded.

"About two minutes after the guy made the call it exploded," Woolston station officer Nick Brown said.

Firefighters arrived to find members of the public giving first aid to two people, who had been using the laundromat at the time of the explosion.

Brown said a small fire was put out quickly, but described the explosion itself as significant. Firefighters found roofing iron from the building up to 20m away in a neighbouring property, he said.

IAIN MCGREGOR/STUFF The explosion caused "significant" damage to the laundromat and surrounding buildings.

"It's been a lot of force behind that explosion," he said, adding it had "blown a massive hold in the roof".

The shop front of the laundromat, which is open 24 hours and self-service, was blown out. The force of the explosion buckled the door and window frames and sent glass several metres.

Adjoining properties also sustained damage in the blast. A wall between the laundromat and Cash Converters was pushed back, and ceiling tiles and light fittings were damaged in both buildings.

IAIN MCGREGOR/STUFF Two people inside at the time of the explosion were taken to hospital with moderate injuries.

The manager of the laundromat, who would not give his name, said he was not at the laundromat when the incident happened.

He said he could not go inside on Monday while the fire investigation was under way. He would not make a decision on reopening until the investigation was completed.

A St John spokesman said two people were taken to hospital with moderate injuries.

A Canterbury District Health Board spokesman said one of the people was discharged from hospital later on Monday.

Fenz fire risk management officer Wayne Hamilton said the cause of the explosion was yet to be determined. Insurance representatives and WorkSafe are also investigating the incident.

Police said they were helping on site and had cordoned off the laundromat.