Aer Lingus Flight 433 bound from Milan to Dublin was put on temporary lockdown when it landed in Dublin on Thursday after a passenger aboard the plane joked about the Ebola virus. Irish law enforcement officials are currently handing the case.

According to the Irish Mirror, a passenger wrote, "Be careful, Ebola" in Italian on a coffee cup. As the Airbus A320 was preparing to land, the passenger handed the cup to a crew member who made the decision to alert the pilot, who contacted authorities on the ground. 

"I suspect it may have been a joke among the passengers and they forgot it was on the cup when they handed it in before landing," an unnamed source told NBC News. "But the crew needs to take these incidents seriously, and they did."

When the flight landed in Dublin around 1 p.m. local time, passengers and crew were held on the plane while authorities investigated the incident. Paramedics were also sent to the plane and discovered that the incident was a hoax. Passengers and crew were released about an hour after landing. 

"Following a minor security incident on board an Aer Lingus flight from Milan to Dublin, passengers were held on board the aircraft after it landed at Dublin Airport just before 1 p.m. today," the Dublin Airport Authority said in a statement. "As a precaution, the incident was fully investigated before passengers and crew disembarked as normal. The incident is now a matter for the gardaí (police)."

Aer Lingus also confirmed that the An Garda Síochána, Ireland's national police service, is now dealing with the matter. The passengers -- three Italian nationals -- involved in the incident are being held at the Ballymun Garda Station for further questioning.