Lynette Horsburgh
BBC News, Merseyside
Police handout
Mr Greener and Ms Jackson died of their injuries shortly after the fire
A man has been arrested on suspicion of double murder after the deaths of an elderly couple in a fire at their home.
Grandparents Peter Eric Greener, 77, who is known as Eric, and his partner Sheila Jackson, 83, died following the blaze at their home on South John Street, St Helens, on Tuesday, Merseyside Police said.
The force said an accelerant was used to start the fire.
A 31-year-old from St Helens was arrested earlier and has been taken into custody for questioning, it added.
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Sheila Jackson died on Thursday
Mr Greener died on Wednesday evening, while Ms Jackson died from her injuries on Thursday morning.
Det Supt Rachel Wilson said: "Although an arrest has been made, I would like to take this opportunity to remind people to pass on information directly to police or anonymously via Crimestoppers.
"Extensive inquiries continue, and to that end we are still appealing for anyone with information to come forward, particularly if you live in the area of South John Street and recall seeing or hearing anything suspicious at around the time of the incident."
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Peter Eric Greener was known as Eric
She said: "Please do not assume what you know has already been reported to us, as we can quickly make that assessment."
She also urged people not to comment or post on social media anything which could jeopardise the investigation.