At least 100 fire-fighters have been involved in a national training exercise to test their response to a large-scale emergency.
The 24-hour training exercises took place in Lincolnshire, Gloucestershire and Merseyside.
Crews in each location were required to rescue colleagues trapped under rubble following an explosion.
The simulation in Kirkby, Merseyside, began at 8am with fire-fighters from Lancashire and Merseyside working with the North West Ambulance Service to free 12 colleagues buried under rubble in a disused swimming pool.
Dan Stephens, Merseyside Fire and Rescue Area Manager, who co-ordinated the event, said specialist technicians worked for weeks to convert the disused Kirkby swimming baths into a hazardous bomb-site.
He said: "This is as realistic as it gets, and is a very very challenging environment. To get to survivors you have to force your way through concrete, enter confined spaces and then make the area safe - it is very difficult."
He said fire-fighters used sniffer dogs to help trace survivors, who were then assessed by paramedics before being freed from the rubble.
Mr Stephens continued: "We are covering a huge area, and looking for survivors is really like finding a needle in a haystack. We are calling this a large-scale explosion, not a terrorist attack, because the cause of the incident would not affect the way we would respond.
"This is one of the largest national training exercises we have done and everything has gone as well as could be expected today, but we will hand-over to a new team at around 8pm and carry on all night."
The other training exercises took place in RAF Waddington in Lincolnshire and the National Fire Service Training College at Moreton-in-Marsh in Gloucestershire.
