Passengers who were due to fly from the airport posted pictures on social media showing the evacuation.

The terminal has now re-opened and Cardiff Airport has apologised for any inconvenience after what it called "minor delays to flights".

The airport located in Rhoose, the Vale of Glamorgan, some 12 miles from the centre of Cardiff, is owned by the Welsh government.

Despite the terminal having now re-opened, the airport has said some flights could still be delayed after the earlier evacuation.

Among the delayed flights, the airport's website listed the KLM flight to Amsterdam due to leave at 10.20am as having departed at 10.38am.

"Unfortunately, we have experienced a safety related incident related to gas in the air conditioning in the building works area within the terminal," said a spokesperson for the airport.

"Safety and security is our number one priority, so the landside area was evacuated whilst our team carried out safety checks."

Read more from Sky News:
Women affected by state pension change 'owed compensation'
Brain-chip patient shown playing chess

Cardiff Airport was used by 857,000 passengers in 2022 - 41.4% fewer than in 2017, according to the Civil Aviation Authority.

A spokesperson for South Wales Police said: "We are aware of an incident at the airport, but it did not require South Wales Police attendance."