Criminals have been manufacturing illegal handguns at a 'large-scale, sophisticated' weapons factory hidden on an industrial estate in a Sussex market town, it emerged today.

The gun factory was uncovered in a warehouse disguised as a gearbox repair business, yards from an Argos and a Screwfix store in Hailsham, East Sussex.

Officers from the National Crime Agency (NCA), often described as Britain's FBI, heard the sound of gunshots coming from the building before they arrested three men earlier this week.

Masked policemen outside an industrial estate unit in Sussex where a gun factory was found

A picture shows the inside of the Hailsham gun factory, hidden on an industrial estate

The NCA said one of the men was tasered during the raid, since which a forensic search of the site has been carried out.

The organisation's Rob Hickinbottom said officers have found around 30 firearms in different stages of production, as well as templates and metal thought to be used to manufacture guns.

He added that his officers believed they have disrupted a group which would have put lethal weapons in the hands of criminals and gangs.

Mr Hickinbottom said he understood that residents of the rural town would be shocked by the discovery, but said criminals seek out quiet industrial units to produce illegal weapons.

The NCA also released these images of ammunition found in the raid in East Sussex

Police have been at the site ever since, and confirmed they have also raided other properties

Mr Hickinbottom said: 'Our investigation is continuing, and much of what we have discovered at this location will now be the subject of careful forensic analysis.

'We suspect that this operation has disrupted a group that would appear to be involved in the criminal production of firearms.

'As a result we have prevented a potentially large quantity of weapons from getting onto the black market and into the hands of criminals.

'I would also like to recognise the superb support and assistance we have had from Sussex Police throughout this operation – their contribution to this investigation has been and will continue to be crucial to its success.'

Business owners based in nearby units told of their surprise at the discovery.

John Saunders, who runs Wealden Installations Ltd, said he arrived to open up at 7am on Monday to find the small corner of the Diplocks industrial estate 'packed with police'.

Officers say the factory was 'large-scale' and they have recovered weapons and ammunition

Mr Saunders said: 'There were armed police watching it. When I learnt what had been found it really surprised me.

'We never saw anything suspicious. It was just a normal business near ours.'

Another nearby business owner claimed to have fitted gearboxes for the workshop.

The 41-year-old man, who asked not to be named, said: 'It was just a normal set-up. I never saw anything unusual.

'It is a complete surprise to hear what was found in this area. Hailsham is a quiet town.

'They supplied the gearboxes and I supplied the time. I worked with the business for about 18 months.'

A police chief said he could understand why residents of the small town would be alarmed

Greg Akehurst, 29, of no fixed address, and Mark Kinman, 63, of Hailsham, were both charged with possessing a firearm.

Kyle Wood, 30, of Littlehampton, was charged with the same offence as well as possessing ammunition.

The trio were remanded in custody and are due to appear at Kingston Crown Court on September 17.