A gang of up to 80 youths were responsible for a seven-hour arson spree across a city, fire chiefs have said.
Scores of firefighters had to deal with 25 separate fires between 1800 BST on Wednesday and 0100 BST on Thursday.
The youths set grassland and rubbish fires along the north side of the River Wear in the Hylton Castle area of the city.
Fire service chiefs say lives were at risk from both the fires themselves and because crews could have been delayed getting more serious emergencies.
Police say no arrests were during the incidents.
Divisional officer John Allison of Tyne and Wear Fire and Rescue Service, said: "This was a tremendous drain on resources.
'Special operation'
"There is the inevitable chance of a delay when we are needed to attend a much more important call.
"Things seem to have flared up in the area over the last couple of evenings and we are working closely with Northumbria Police and the area's arson task force to try and catch these culprits."
Chief Inspector John Brady of Northumbria Police, added: "We have set up a special operation which will be ongoing over the next few nights in which we will be on patrol with CCTV cameras in an effort to catch these youngsters.
"If we get evidence of youths carrying out the kinds of activities they were last night, we will take very serious action.
"And I am sure the courts will take a very dim view as well."