HUNDREDS of emergency services staff are due to take part in a massive mock search and rescue mission on Dartmoor today.

Police, the Army, fire crews, the Dartmoor Rescue Group and Exmoor and Cornwall mountain rescue groups will be involved in the exercise.

A team of cadets will play the roles of casualties.

The 'live' exercise is due to run from about 10am until 4pm.

The day is designed to test each agency's expertise during search and rescue operations, and the exercise is based on a Ten Tors training weekend.

During the scenario, extreme weather leads to a large number of 14- to 18-year-olds becoming lost on the moor.

There are a number of casualties, 43 people are unaccounted for and, due to the adverse weather conditions, the search and rescue helicopters are not usable.

Colin Rockey, special operations manager at Devon and Somerset Fire and Rescue service, said: "This is a good opportunity to work with our sister emergency services in a realistic and testing environment.

"When large-scale emergencies occur it's important to ensure that we all use the correct resources in both an effective and efficient way.

"This event will allow us to test those principles in order to ensure that in a real situation everyone fully understands what's expected of their own agency."