According to Essex Fire Service, around 22lb (10kg) of explosives were involved in the blast, which occurred at a weapons testing centre at MoD Shoeburyness, near Southend.
The weapons testers were freed by MoD officers in an armoured personnel carrier, but there were no injuries.
Five fire crews attended the incident, which happened at around 11am today.
A spokesman for QinetiQ, the private defence contractor that runs the Blackgate Road munitions centre, said:
"No-one was hurt in the incident at our environmental test centre and we are conducting a full investigation into what happened as is part of our standard safety procedures."
The Southend Airshow, which was axed by the council in March in a bid to save £10.5 million pounds from its budget, is to be brought back next year by volunteers. A non-profit organisation has been set up by locals who aim to raise £300,000 in order to put on the event in September 2014.
Now, a sight you don't usually see on the roads - a fleet of one London taxi cabs in convoy. But it was all for a very special reason. They were taking three hundred deserving children for a very special day out in Southend. Click here to see the report from Jenny Line.
Included in the report are interviews from taxi driver Levy Raymond, teacher Andrew Rigby, Event Organiser Susan Angel and Andrew Renton, the Grandson of the event's founder.
Police are looking for a 19-year-old man who has absconded from Southend Crown Court. Ricky Kerry ran from the dock of the court in Victoria Avenue just as he was being sentenced to 28 months for robbery.
Police have launched a manhunt after a 19-year-old fled a court dock as a judge was about to send him to jail. Unemployed Ricky Kerry ran from the dock at Southend Crown Court after being sentenced to 28 months in prison for robbery.
Essex Police say he made off on foot at just after 12.45pm in the direction of Baxter Avenue. It is understood that Kerry, of Jones Close, Southend, escaped through heavy double doors at the entrance to the court and down two flights of stairs.
The force said Kerry was being sentenced for a robbery in Sutton Road, Southend, in April in which he punched a man and took his mobile phone. Anyone with information should contact Essex Police on 101
This is the sight that greeted a honeymoon couple when they got back to their home in Southend.
Steve and Hayley O'Rouke's terrace house was given an unexpected Mr Blobby style makeover.
Mr O'Rourke's brother Russell got to work Crinkley Bottom-style in a revenge prank after he'd returned from his own honeymoon to find a brick wall built across his drive.
A newly-wed couple returned from honeymoon to find that their home had been painted bright Pink in the style of Mr Blobby.
The Daily Mirror reports how Steve and Hayley O’Rourke, 32 and 31, from Southend discovered the prank after their two week honeymoon
The groom’s brother Russell, 35, planned the Mr Blobby-style paint job in revenge for a similar joke six years ago.
See full story here http://www.mirror.co.uk/news/uk-news/mr-blobby-home-prank-honeymoon-1903094
We would urge anyone with information to come forward. Such behaviour is totally unacceptable and will not be tolerated. Our staff have a right to go about their jobs without facing fear, intimidation or abuse of any kind.
Anyone with information is asked to contact to British Transport Police on 0800 40 50 40 quoting background reference B7/LNA of 16/04/2013. Information can also be passed to the independent charity Crimestoppers, anonymously, on 0800 555 111.
Around 5.15pm, a man, who had verbally abused two women outside Southend Victoria station, followed them through the ticket barriers and onto the station platform. The women reported the man’s behaviour to a member of station staff, who confronted him and asked to show a valid ticket. As he was only in possession of a child’s ticket, a member of staff escorted him out from the train, and towards the station entrance. At the ticket barriers, the man began to verbally abuse the staff member, before punching him in the chest and making off from the scene.
British Transport Police is appealing for information after a member of station staff was assaulted on board a train at Southend Victoria station.
Investigators have released CCTV of a man they would like to speak to in connection with the incident, which took place on Monday, 25 March.