Paul Mescal was pictured allegedly sniffing a suspicious substance from a bag as he partied with pals at Glastonbury on Sunday.
According to The Sun the Irish actor, 28, used a key as a scoop to raise the unknown material to his nostril while dancing in the crowd during US band The National's late night set.
Paul was dressed casually and donned a baseball cap, with one onlooker telling the publication the actor 'didn't seem to care' if anyone could see him.
Saying: 'Paul looked like he used a key to scoop some substance out of a bag which he lifted to his nose and sniffed.
'He did it once then he dipped the key back into the bag and lifted it to his nose and sniffed again.
'Paul didn't seem to care if anyone could see him. He was dancing and laughing with his friends.'
MailOnline have contacted Paul Mescal's reps for comment.
Earlier in the day Paul sent fans wild by singing Shania Twain's iconic line 'Let's go girls!' ahead of her performance at the festival.
He was among the stars who headed to Worthy Farm for the annual music festival and was captured ahead of Shania's Legends Slot on Sunday.
In a now widely-shared video whoever is filming him begins the beat to her hit Man! I Feel Like A Woman! - as he finishes off the famous line with: 'Let's go girls!'
He was clad in his usual short shorts attire for the festival which he teamed with a grey T-shirt and cap.
The BBC shared the video on their Instagram and Shania herself commented saying: 'Love it!!', along with several laugh crying emojis.
Fans were loving the clip as they commented under the video saying: 'He's too cute!',
Fans were loving the clip as they commented under the video saying: 'He's too cute!',
'Quality content', 'Have I watched this 100 times? Yes', 'Why's he so cute', 'Love him!' .
It comes after Paul showcased his rippling muscles as he took to the Coliseum in first offical snaps from much the anticipated Gladiator sequel
Due for release later this year, the Irish , takes on the role of Roman Empire Lucius Verus, the grown-up son of Lucilla, portrayed as a child in the Oscar-winning original from 2000 starring Russell Crowe.
Paul donned a full suit of armour, complete with breast place and leather kilt, bearing a striking resemblance to his predecessor Russell - who will not appear in the sequel.
The Normal People star then went shirtless for a dramatic scene where he appeared to be preparing for battle before taking on blood soaked Pedro Pascal, 49.
Describing his character to Vanity Fair Paul said: 'He's a very, very good general, which can mean a very good killer.'
In another action packed moment the duo went head to head with Paul diving into the air while Pedro's character looked terrified as he lost grip of his sword.
The Last Of Us' Pedro plays Roman general Acacius, who trained as a gladiator beneath Russell's character Maximum.
With the actor saying: '[Acacius] learned from the best, so of course this code of honour is ingrained into his training and into his existence. But at the end of the day, he's a different person. And that can't change who he is.
Before teasing: 'Maximus is Maximus, and that can't be replicated. That just makes Acacius capable of different things.'
Denzel Washington, 69, was also pictured for the first time as Macrinus, dripping in gold he plays an arms dealer who lives lavishly and keeps gladiators for sport.
