Health authorities have issued a warning over a potentially lethal drug after the death of a young man and the hospitalisation of four other people in Donegal this morning.

Gardaí investigating the death of a 22-year-old man at a house in St Johnston, Co Donegal.

An ambulance was called to the flat on Main Street in the town in the early hours of this morning and four other people were taken to hospital.

The four people were an 18-year-old woman, and three men aged 18, 22, and 25. 

The group are believed to have been attending a party at a house on Main Street.

The HSE Public Health Department in the North West issued a statement stating that it has "become aware of a number of people with serious illness requiring medical treatment/intervention as a result of taking substances including an ecstasy-like substance known as Double Cross and/or Double Black."

It is advising people not to take these substances and said that people who take drugs "should be specifically warned of potential dangers linked to these substances or using drugs in combination" and said it is important that anyone displaying negative side effects following the use of drugs seek medical help immediately.