Updated

Four alleged smugglers are accused of using unusual vehicles to carry drugs into Britain — a fleet of ambulances.

A joint British and Dutch investigation put the brakes on the scheme this week when police arrested four Dutch nationals — two of them wearing paramedic uniforms — and seized 270 kilograms (nearly 600 pounds) of heroin, cocaine and amphetamines hidden in secret compartments in an ambulance in the city of Birmingham.

Dutch detectives said Friday the stash had a street value of 10 million euros ($11.3 million).

In a statement, Brent Lyon of Britain's National Crime Agency calls the smuggling "an audacious plot" in which suspects posed as paramedics "to avoid unwanted attention" as they entered Britain.

Police raids in the Netherlands following the arrests found 10 more ambulances.