Three people have suffered "serious side-effects" from taking a drug they thought was ecstasy at Staffordshire's V Festival, prompting a police warning.
The blue tablets, known as "Blue Ghost", have left the three people at the music event requiring emergency medical treatment and police have seized a small number so far.
A Staffordshire Police spokesman said: "Emergency teams have treated three people 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.
"If you see anything suspicious contact the on-site police or security immediately - officers are investigating the incidents and have already seized a small number of tablets called 'Blue Ghost'.
"If you have taken any of these tablets - contact emergency teams immediately."
Anyone with any information about drugs can also call Crimestoppers on 0800 555 111 or in an emergency 999.