One person has been taken to hospital with 80% burns following a large blast in the Shaw area of Oldham, the North West Ambulance Service has said.
Greater Manchester Police said the explosion happened in Buckley Street shortly after 11:15 BST.
Police, fire and ambulance services are at the scene and there were “possibly people trapped”, Greater Manchester Fire Service said.
Police and the fire service said it was a suspected gas explosion.
A fire service spokesman said: “The control room has received numerous calls from members of the public and the initial information from the public is that it involves a number of terraced properties.”
The ambulance service said the burns victim had been taken to Wythenshawe Hospital, Manchester.
The blast is believed to have damaged two terraced houses.
A cordon is in place and a police helicopter is circling over the damaged properties.
Eye-witnesses half a mile away reported their homes were shaken by the explosion.