Two crew members remained in hospital on Tuesday after a Swiss airlines flight was forced to make an emergency landing the previous evening due to smoke in the cockpit and cabin, the company said, reports AFP.

An Airbus 220-300 aircraft which had 74 passengers and five crew on board was flying from Bucharest to Zurich late on Monday when Swiss said it was forced to land in Graz after suffering engine issues and smoke appeared in the cabin and cockpit.

"Two cabin crew members are currently still in hospital," the airline said in a statement.

"One cabin crew member had to be flown by helicopter to a hospital in Graz yesterday and is in intensive care; his condition remains unclear," it added.

Passengers who had been hospitalised have since been able to leave the hospital, Swiss said.

The airline, a subsidiary of Germany`s Lufthansa, said it transported 63 passengers to Zurich on Tuesday aboard a special flight and was assisting passengers who still remained in Graz.

Swiss added that relevant authorities were investigated the cause of the incident and did not provide any additional details.