Police are concentrating their inquiries on a mystery liquid poured into the home of the 17-year-old girl who suffered burns in an explosion in South Harrow.
The liquid was poured through the letterbox of the ground floor flat at 21 Stanley Road between 9am and 10.53am on Wednesday, May 7.
Less than 12 hours later, an explosion destroyed number 21 and neighbouring properties, number 19 and number 23.
A 17-year-old girl had made a 999 call to police at 10.53am that day from her home, number 21, to report a group of girls outside her house. Officers say she did not at the time need help.
A Pakistani man, believed to be 26-year-old Emad Quereshi, died in the blast.
He was in number 23 when it collapsed, with another 26-year-old, visiting from Pakistan, who was injured in the explosion and is now in hospital.
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The 17-year-old girl, who lives alone at the flat, suffered flash burns in the blast. Police say her burns are not chemical burns.
It is understood both the girl and the injured 26-year-old are conscious and have been interviewed by police.
Nobody else was injured in the explosion.
Police are appealing for witnesses to the events leading up to the blast.
Anyone with information can call the Met's incident room on 0208 247 7911.
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