A firefighter was injured last night and several of his colleagues were treated for shock following an explosion at a derelict house in Newry.
The explosion occurred at around 7pm, minutes after fire and rescue crew arrived to tackle a blaze at the building on Sinclair Street.
Northern Ireland Fire and Rescue Service station commander Andy Sinclair said the fire crew was tackling the blaze from the outside of the house when metal shutters, which were covering the windows, blew out and knocked two officers off their feet.
"One of the officers was taken to hospital for treatment and seven other personnel were sent away for check-up because they had also been involved in the incident. After the explosion, four more appliances attended the incident.
"We evacuated the area and a number of families had to leave their homes," he said.
Mr Sinclair added that the cause of the explosion is not yet known and that the scene will be investigated later today by PSNI scenes of crime officers.
"At the minute we cannot work out why there was an explosion. We thought it may have been a gas cylinder but there were a number at the scene and none looked like they were involved in the fire," he said.
PSNI officers assisted at the scene yesterday evening and a 200-meter exclusion zone was introduced. The road was reopened at 10pm.
The cause of the fire is not yet known.
Deputy Mayor of Newry and Mourne, councillor Charlie Casey, said it was an extremely serious and dangerous situation.
He added that the council had made the sports centre available for any residents who were evacuated.
"It was a fairly large blaze and there was a lot of black smoke around the area. The emergency services left after 9pm and residents were allowed back into their homes but part of the are remained sealed off.
"Thankfully, none of the firefighters were badly injured. The Northern Ireland Housing Executive has sent a contractor in to demolish a building that has been deemed unsafe."