Police launched a murder investigation following the death of a 71-year-old woman in an arson attack.
Hameeda Begum died following the house fire in Bolton, Greater Manchester, seven days ago.
The fire began when a wheelie bin was set alight outside her terraced home in Little Holme Walk, Great Lever, at around 11.30pm.
Firefighters rescued Mrs Begum but she later died in hospital. They also rescued her husband, jeweller Chifhty Mumtaz, their daughter Saima Main, 24, and granddaughter Alana Main, aged five.
Mrs Main is being treated at Wythenshawe Hospital and her daughter is being treated at a specialist burns unit in Leicester. They are both in a critical condition.
Three firefighters who rescued the family also received burns. One of the officers suffered 50 per cent burns to his lower back and legs, and serious burns to his hands.
Police have refuted media reports that the fire was a revenge attack.
Last year Mr Mumtaz gave evidence against four members of Manchester's notorious Gooch Close gang after they stole £10,000 worth of jewellery from his store.
His evidence culminated in lengthy sentences for the four men, who had pleaded guilty to robbery.
A Greater Manchester Police (GMP) spokeswoman said today that they were not following this line of enquiry in connection with the murder.
Detective Superintendent Sam Haworth, from GMP's major incident team, said: "We are treating this fire as arson and therefore the tragic death of Hameeda will be treated as murder.
"Two people still remain critically ill as a result of this fire and it is vital that we find out who is responsible for starting this devastating blaze.
"I know the community are as committed as we are to finding out who did this, and we still have a dedicated team of detectives working on this case.
"I still want to hear from anyone who was in the vicinity of Little Holme Walk between 10pm and midnight last Monday, any information could prove vital."
Anyone with information is asked to call the major incident team on 0161 856 2197 or Crimestoppers anonymously on 0800 555 111.Reuse content