Gardaí investigating the death of a 24-year-old man who collapsed on board an Aer Lingus flight are hoping a postmortem on Monday will establish how he died.

The Brazilian man was travelling on a flight EI 485 from Lisbon to Dublin yesterday afternoon when he became agitated and, in the course of being restrained, bit a passenger assisting the crew.

It is understood the man was subdued and handcuffed, but some time later he collapsed and was attended to by a doctor who advised the captain he was in a critical condition.

A passenger on the flight told Cork’s 96FM how he saw the Brazilian man “shaking violently” as he suffered what appeared to be a number of seizures.

“The noise he was making was like something that I’d never heard before and wouldn’t like to hear again,” said the male passenger, describing the sounds as “guttural”. “It was like a deep anguish, that is the best way I can describe it. It was very, very troubled.”

The plane’s captain contacted the Irish Aviation Authority’s North Atlantic Communications Centre at Ballygireen, Co Clare to say he had a medical emergency.

The flight diverted to Cork Airport and landed at about 5.40pm and the man was attended by paramedics but pronounced dead soon after.

His body was removed from the airport to Cork University Hospital (CUH) where assistant state pathologist, Dr Margot Bolster is due to carry out the postmortem.

Gardaí arrested a woman they believe was travelling with the man on suspicion of drug trafficking.

The 44-year-old Portuguese woman was arrested after gardaí searched her luggage at Cork Airport and found two kilos of a powdered substance which they believe are illegal drugs.

The woman was detained under drug trafficking legislation and taken to Togher Garda station for questioning while the powder substance found in her luggage has been sent to the Forensic Science Ireland laboratory at Garda headquarters for analysis.

It is understood the woman, believed to have been sitting beside a 24-year-old Brazilian man who died on the flight, came forward after the man was pronounced dead to say that she knew him.

Violent

Gardaí are hoping the postmortem will establish whether or not the man may have ingested a substance which led to him becoming agitated, violent and then unwell on the flight.

The male passenger who was attacked and bitten in the incident was taken to CUH and treated for his injuries.

Gardaí took witness statements from the six crew members and 168 passengers who were on the flight, which left Lisbon at 3.30pm.

It is understood passengers were later bussed to Dublin but the plane was detained by gardaí at Cork Airport and is being treated as a crime scene by investigating officers.

Garda technical experts will carry out a full forensic examination of the plane on Monday.

It is understood the man, who was sitting at the rear of the plane, became agitated midway into the two and a half hour flight before attacking a passenger seated near him.

The airline issued a statement on Sunday night which confirmed “Aer Lingus flight EI 485 Lisbon to Dublin, diverted into Cork due to a medical emergency on board.

“There were 168 guests and six crew members on board. The flight landed safely at 17.40, local time.”

The company said it was assisting gardaí with their inquiries.

Under the Air Navigation andTransport Act 1998, the man’s death becomes a Garda matter once the plane has taken off from Lisbon Airport as the plane is registered as an Irish aircraft.

Gardaí were last night trying to contact the dead man’s family through the Brazilian Embassy in Dublin.

Were you on flight EI 485? Send any information or updates to newsdesk@irishtimes.com