One Direction singer Liam Payne had a cocktail of hard drugs in his system when he plunged to his death from the third floor of a hotel balcony in Argentina, according to reports.

Multiple US media outlets are reporting partial results of toxicology tests after the pop star’s tragic death in Buenos Aires last week.

Payne was under the influence of multiple substances, including “pink cocaine”, cocaine, benzodiazepine and crack, reported America’s ABC News, quoting sources.

WebMD says pink cocaine is a “new designer drug” that is typically a powdery mix of ketamine and other illegal substances likely dyed with food colouring.

The drug, which originated in Colombia, sometimes has a sweet smell, like strawberries.

“Pink cocaine hasn’t been around very long, so researchers don’t know much about the long-term effects it may have on people who use it,” says WebMD.

Sources said an improvised aluminium pipe for drug use was found in Payne’s hotel room, writes the ABC.

TMZ added that police found a bottle of alcohol and prescription medications, namely, anti-anxiety medication.

Preliminary autopsy results released on Friday (AEDT) revealed the troubled star suffered 25 injuries compatible with a fall from a height, including fatal head injuries and internal and external bleeding.

Buenos Aires police found his hotel room in “complete disarray”, with pictures published in Argentinian media showing a smashed television, white powder and tin foil.

Payne’s death sent shockwaves through the music industry and left fans heartbroken, with people gathering in cities around the world to mourn the singer.

One Direction fans, called Directioners, left tributes in London, Glasgow, Paris, Sydney and New York as they celebrated the life of the 31-year-old who died last Thursday (AEDT).

In London’s Kensington Gardens, they clapped and sang after gathering near a statue of Peter Pan, the fictional boy who never grew up created by JM Barrie.

The mourners, mostly young women, left heart-shaped balloons, photographs and flowers at the base of the statute, which sits next to a narrow path next to a waterway known as The Long Water.

Mindful of the crowds in the limited space, organisers asked fans to leave their tributes then move away to allow others to approach.

Fans Lauren Anderson and Natasha Bradley, both 23, said they wanted to be with others who shared their grief.

“Your parents, they don’t really understand how much [One Direction] really meant to you growing up,” Bradley said.

The vigils followed others outside the Casa Sur Hotel in the chic Palermo neighbourhood of Argentina’s capital immediately after Payne fell from his third-floor hotel room.

The four surviving members of One Direction issued a joint statement saying they were “completely devastated” by the death of their bandmate.

One Direction rose to worldwide popularity soon after the band was formed in 2010 from five young singers who auditioned for the British version of The X Factor TV talent show.

The band broke up in 2016 after producing five albums that sold more than 70 million copies.

-with AAP