text: A former commander of the Metropolitan Police's elite Flying Squad has said the Hatton Garden gem heist could be linked to the huge underground fire which ripped through London last week. The massive fire started  last Wednesday and took more than 24 hours to put out. John O'Connor, a highly experienced former police detective, has claimed the major power outage and the proximity of the multi-million burglary was far more than a coincidence. Scroll down for video . A gang of criminals broke into the Hatton Garden Safe Deposit Ltd over the Easter Bank Holiday weekend . It came shortly after firefighters  battled a major fire in Holborn - just 500 metres from the raid site . Speaking on LBC, Mr O'Connor said: 'Yeah, I think that probably was deliberate. 'I've never heard of an outage of electricity like that causing a fire that lasted as long as that. That seems to me as too much of a coincidence.' He also said that in his opinion, to succeed with such a complicated and ambitious crime, the gang must have had some inside help. He added: 'You're gonna have to have a detailed layout of the whole of the business. So clearly they got that from somebody on the inside.' He later told Sky News: 'You've got a major strong room, there's no sign of a forced entry, they've apparently been able to abseil down the lift shaft to get access to the vault - I just find it astonishing that it was that easy. 'The fact that there is no sign of forced entry, what does that mean? That someone left the door open? That someone left the windows open? Former head of Scotland Yard's Flying Squad, John O'Connor, pictured, said the Holborn fire and the raid could be linked . 'It smacks all the time of inside aid, all of the way through it. This doesn't look to me like a genuine sort of smash and grab raid by determined criminals, this looks like they've had accomplices on the inside.You wouldn't go to attack a building like that unless you knew you could gain access.' The London Fire Brigade said they do not believe that the blaze was caused deliberately. Fire experts said their initial assessment showed that the fire was caused by an electrical fault in the Victorian tunnels running below ground, damaging an eight inch gas main which ruptured and fuelled the flames. Fresh details of the daring heist emerged yesterday as police forensic teams continued to sift through the rubble in the vault. It is believed an alarm was triggered when the professional gang broke into the building in the heart of London’s jewellery district. A security guard is understood to have made a cursory check of the property on Good Friday before leaving when he found nothing untoward. Police have refused to say whether officers were despatched to investigate around the same time. The gang used a heavy-duty drill weighing 77lb to bore through a reinforced 7ft concrete wall to reach the vault. When the raid was discovered on Tuesday, police discovered cheaper jewels left strewn amid a large heap of rubble in the vault. Detective Chief Inspector Paul Johnson of the Flying Squad said: ‘I’d say it’s a sophisticated offence and clearly it would have taken some pre-planning. It’s organised. It’s people who have planned it and they know how they were going to go about it. ‘I would imagine that the pool of people [who could carry out the heist] is quite limited.’ The  fire started underground just several hundred yards from where the heist took place a few days later . The gang is thought to have hidden in an office before abseiling down a lift shaft and drilling into a vault . It has also emerged that celebrities and Premier League footballers could be among the victims of the thieves. A source told the Daily Mail: ‘At least two of the jewellers have gems in the vault which have been bought by footballers and celebrities. They are waiting nervously to find out if they are among the victims.’ Mr Johnson described how the gang gained access to one of the offices on the second floor of the building where they disabled the lift before climbing down. Once in the basement the thieves forced open the lift doors to get close to the vault. They used a £3,500 Hilti DD350 drill, which is commonly used on large construction sites, to drill through the reinforced concrete wall to reach the vault. Joel Vinsant, secretary of the Drilling and Sawing Association, said that even with high-tech equipment, it may have taken hours for the thieves to drill through the concrete. He said: ‘What they might have done is to bore several holes with a rig-based drill until they had made a space big enough to get through, rather than boring one hole and breaking through. It could have taken up to an hour per hole.’ Detective Chief Inspector Paul Johnson of the Flying Squad, speaks to journalists outside Hatton Garden Safe Deposit Ltd today following last weekend's burglary in London . Police yesterday revealed the thieves used a Hilti DD 350 drill to get through the two-metre thick vault walls . During the raid the gang used an angle grinder and crowbars to force their way into 70 deposit boxes to steal the gems and cash inside. They then made their escape before employees arriving for work on Tuesday spotted the raid. Mr Johnson added: ‘The scene is chaotic. The vault is covered in dust and debris and the floor is strewn with discarded safety deposit boxes and numerous power tools, including an angle grinder, concrete drills and crowbars. ‘There is no sign of forced entry to the outside of the building. We are in the process of identifying the owners of the safety deposit boxes and contacting them to take statements and find out what has been stolen.’ He said his team had only just reached the vault because of the amount of debris at the scene. Mr Johnson added: ‘It’s got to be a slow, painstaking and methodical forensic process to get in there.’ Experts fear the thieves may have already smuggled the jewels out of the country and are planning to cut up the larger gems to make it easier to sell them on the black market. One jeweller who rents a deposit box said police have identified the owners of 30 boxes which had been broken into. Furious jewellery dealers today accused the manager of the safe deposit of 'gross negligence'. Pictured: Felix Stephens (left) and Gerald Landon (right)
target: The Holborn fire broke out on Wednesday just 500 metres from the vault .
  Raiders entered the Hatton Garden vault some time over the weekend .
  An alarm sounded on Good Friday, but the vault was not checked .
  Former Flying Squad chief John O'Connor believes there could be a link .