A family made an emotional appeal today to help catch the killer of a man who died after a firework was pushed through his letterbox.

Meanwhile, police in Darlington are hunting youths thought to be responsible for posting a burning sparkler through the letterbox of a house in the town.

Arthur Lonsdale died in hospital of respiratory failure caused by smoke inhalation after fire swept through his home in Westerham Close, Witherwack, Sunderland, last Thursday.

The 52-year-old former locksmith, known locally as 'Arky', died in hospital on Saturday from respiratory failure.

His tearful mother Elsie and sister Carol yesterday attended a press conference, where a statement was read out by Detective Inspector Rob Coulson on their behalf.

They said: "It is really terrible what happened and we are devastated.

"Someone must know who did this. Arky did not deserve this - no one deserves to die this way.

"We would like to appeal to people living in the area to come forward and we hope this appeal will prick someone's conscience.

Det Insp Coulson, said: "We still have no motive for what happened and are looking at every possibility, including the fact that Mr Lonsdale could have been victimised and harassed in the past."

Police in Darlington said a lit sparkler was pushed through the letterbox of a woman's home in Arundel Drive, in the Cockerton area of town, at about 7.45pm on Wednesday.

Acting Inspector Alison Jackson said the incident is being treated as arson after a set of net curtains was set alight.

"If the woman hadn't heard the letterbox and gone to investigate, the fire could have been a lot worse," she said.

"We are treating this very seriously - because there was someone in the house we are looking at arson with intent to endanger life.

Youths don't think about the potential danger - to them it is just a joke. They don't think about the fact there could be someone in the house who could have been killed.

Less than two weeks ago Lindsay Price and her two children were forced to flee their home in Marrick Avenue, Darlington, after a firework was pushed through their letterbox.

Anyone with information concerning Mr Lonsdale's death should call 0191-454 7555, ext 65017. Police investigating the Darlington incident can be contacted on (01325) 467681.