David Hultman, who has been leading the fire service's investigation since December said: “We have been looking at different possibilities but a deep fryer has never been a theory that we have been working on”.
“A deep fryer would probably be located in the kitchen and yet this is the only place with just secondary [less severe] damage from the fire…so it is very unlikely given what we have seen from looking at the soot and particles on the walls,” he added.
The investigator’s comments come after a police source told local newspaper Eskilstuna-Kuriren on Monday that an overheated deep fat fryer was the source of the blaze.
Initial reports suggested that the fire started after someone threw a burning object into the building in the city of Eskilstuna, some 90 kilometres west of Stockholm, leading to much speculation that the alleged attack was an anti-Islamic hate crime.
Around 70 people were in the mosque when the fire took hold and many of them fled through windows to escape the fire.
Some campaigners used the rallies to blame the rise of the nationalist Sweden Democrat party for increasing Islamphobia in Sweden.
Police in Eskilstuna would not confirm the deep fat fryer claims on Monday and said the investigation was still ongoing.
Local media reports on Tuesday suggested that Eskilstuna police were blaming police in neighbouring Västmanland for the leak.
“As far as I understand, this ‘information’ about the fire did not come from police in this town who have been working on this case. I am not really sure who came up with this,” Hultman told The Local from Eskilstuna.