Four teenagers were today arrested on suspicion of murdering a man who died in a blaze that was believed to have started when a lit firework was pushed through his letterbox, police said.

The youths, one aged 17 and three 15-year-olds, were arrested in connection with the death of Arthur Lonsdale.

The former locksmith died in hospital two days after a Little Brother rocket was allegedly shoved through the letterbox of his home in Westerham Close, Witherwack, Sunderland, on October 28.

Mr Lonsdale, 52, who was well known locally as Arky, died from respiratory failure caused by smoke inhalation.

Last month two women, aged 27 and 57, were released on bail after being arrested on suspicion of illegally supplying fireworks to under 18s.

Police said they needed to speak to witnesses who were in the vicinity to where Mr Lonsdale lived on the night of October 28.

Detective Superintendent Steve Wade said that despite arresting four local youths he still wanted to speak to anyone who was in the area between 8pm and 9pm and had not already come forward.

''Any information, no matter how small or insignificant it may seem, could help our inquiry,'' Mr Wade said.

Mr Lonsdale, who lived alone, was a cat lover who provided a refuge for abandoned animals and a number of cats he was caring for died in the fire.