Emergency crews have treated three music fans at Britain's V Festival after they suffered "serious side-effects" from drugs.

The revellers reported taking a blue pill they believed to be ecstasy before falling ill at the event in Staffordshire, England on Saturday (16Aug14).

Police are investigating the incident and have seized a small batch of the drug, dubbed 'Blue Ghost', on the festival site.

A statement from Staffordshire Police on Saturday reads, "Emergency teams have treated people this evening who took a blue tablet they believed to be ecstasy at V Festival in Weston Park. All had serious side-effects after taking the tablets and needed urgent medical treatment."

Justin Timberlake and Ed Sheeran are due to close the two-day event in Staffordshire on Sunday (17Aug14), while The Killers and Lily Allen are set to perform at its twin leg in Chelmsford, England.