Police confirm EDL graffiti found at site of blaze in Muswell Hil, London, as fears increase of reprisals after Woolwich murder

Police are treating a fire that badly damaged an Islamic community centre and mosque as suspicious amid continuing fears of reprisals after the Woolwich murder.

Specialist officers from the Metropolitan police's counter-terrorism command are leading the investigations in to the incident at Muswell Hill, north London.

Police have also confirmed that graffiti reading "EDL" – which may stand for English Defence League, a far right group – was found at the building, while neighbours reported hearing a loud explosion in the early hours of Wednesday morning.

A large area has been cordoned off with officers conducting a fingertip search in surrounding streets.

Scotland Yard said: "The cause of the fire is currently under investigation and is being treated as suspicious at this stage … Graffiti reading EDL has been found on the building. Police are investigating any potential connection between the graffiti and the fire."

There have been no arrests.

The decision was made to hand the investigation over to Scotland Yard's counter-terrorism command because of a possible link to domestic extremism.

The unit is said to have the capability and expertise to establish whether the graffiti is a true indicator of the motivation behind the arson attack, or a false lead.

Until now the EDL has been seen as primarily a public order issue for police. The investigation into the blaze in Muswell Hill will examine whether there are any links to the EDL. "If the EDL are involved, the counter-terrorism command will establish if it is linked to them and what that means," said a source.

Firefighters were quickly suspicious about the blaze and told police of their concerns, which has led to detectives treating the fire as a deliberate act.

Six fire engines and about 35 firefighters were battled the blaze early on Wednesday. The building houses the al-Rahma Islamic Centre and the Bravanese Centre used by members of the local residents with links to Somalia. It took more than an hour to bring the fire under control. Two neighbouring properties were evacuated.

London fire brigade said the entire building was damaged, and there had been a "partial structural collapse". A woman from a neighbouring property was treated for shock at the scene by ambulance crews.

Chief Superintendent Adrian Usher said. "I have spoken to community leaders and assured them that a thorough investigation is being conducted.

"The safety of our communities is always our priority and we are consulting widely, offering our support and reassurance. All communities can be confident that they have our support and I can be contacted personally to answer their concerns."

Mohamed Elmi, chairman of Somali Diaspora UK, said his organisation had received around 100 calls from people associated with the centre.

"Fifty per cent of the people who have been in touch are from people who say they are scared – scared to leave their homes or women scared to wear their hijabs in the street … People are really shaken up by this."

But he said that if the aim of those behind the fire was to divide people they would fail, adding: "We have to be calm and strong and not let these people win."

Ahmed Sheiba had been a regular at the Islamic centre for the past decade and had arrived for a meeting on Wednesday morning to find it all but destroyed. "We are just sad, to be honest – what can we do?" he asked.

Sharon Sturgess, who lives near the centre, said she had woken to the sound of fire engines at around 3.30am.

"It was a youth club when I was a girl and we all used to go there … You just don't think this sort of thing is going happen in your own area, do you?"

One witness, who wanted only to be known as Nurein, told the London Evening Standard: "I was woken up by loud noises and then soon I could smell the fire. I went outside and it was really bad. There were huge flames and lots of smoke. There were several fire engines and I think even a helicopter. It was terrible. This will really shake the community up."

Mohamed Ali, of the Somali charity BritSom, said he believed the incident was linked to the Woolwich attack in south-east London. "The place has been absolutely destroyed. The community is shocked and very distressed because they have been here in peace for the past 20 years.

"We are a peaceful community so I do not know what has brought this on. The building is a centre for the community, it is used as a mosque, a gathering place for Somalis to meet up and as a school for young children to learn Arabic.

"This is shocking but it will not break the community as a whole. I would appeal to the people who did this to come and sit down with us and have a dialogue. That is the only way forward."

According to Faith Matters, a group which monitors anti-Muslim hatred, there had been 12 attacks on mosques since Drummer Lee Rigby was killed in Woolwich two weeks ago. The most serious so far has been the attempted fire bombing of the Grimsby Islamic Cultural Centre while people were inside.

The mosque attacks are among 222 anti-Muslim incidents reported to Faith Matters' Tell Mama project in the last fortnight, well above the normal average of four to eight a day.

The mayor of London, Boris Johnson, said: "I was shocked to learn of the fire at the Bravanese community centre in Muswell Hill. There is no place in an open, tolerant and diverse city like London for hate, for prejudice, for violence.

"I would urge people to give the police the time and space to investigate this incident fully. I have no doubt the Met will bring those responsible to justice. London is a city built on the strength of its communities. Londoners will see this for what it is – cowardly, pathetic and utterly pointless."

Police also said there had been a second graffiti attack on the Bomber Command memorial in central London. The words daubed on the memorial called for Rigby's killers to be hanged. In a previous attack the word "Islam" was written on the memorial.

The RAF Benevolent Fund (RAFBF) responsible for the upkeep of the structure, would not confirm the wording of the graffiti but said: "We are extremely disappointed and saddened that the Bomber Command memorial has once again been subjected to vandalism."

The charity added that the cost of removing last week's graffiti is expected to be about £10,000.