Hundreds of paramedics, firefighters and police are taking part in a simulation in the port of Dover.
Crews will be cleaning up a simulated chemical spill from a lorry which has accidentally dropped its hazardous cargo.
Officers are keen to stress that this is an exercise so residents should not be alarmed if they hear sirens in the area.
More top news
Kind-hearted families have raised thousands for a vital heart machine at Southampton General Hospital. We've been hearing their stories
Actors Sir Anthony Hopkins and Mark Wahlberg have been pictured in Gosport, filming for the new Transformers blockbuster.
Thursday night's weather for the east of the region