Up to 30 passengers on board a domestic flight in India suffered nose bleeds and headaches after cabin crew failed to flick a switch to regulate cabin pressure.

Jet Airways’ flight 9W 697 from Mumbai to Jaipur, a tourist destination and capital of Rajasthan state, had 166 passengers on board when it turned back shortly after takeoff on Thursday (local time).

Once it had landed back in Mumbai, passengers were given first aid in the airport terminal. In a statement released via Twitter, Jet Airways said five people were taken to hospital for further treatment but had since been released.

New Delhi Television reported the incident occurred because of crew error.

“During the climb, the crew forgot to select a bleed switch due to which cabin pressure could not be maintained,” an aviation regulator Directorate General of Civil Aviation officer said.

Frightened passengers were quick to post videos on social media of the mid-air emergency, showing oxygen masks dropping from overhead compartments.

One described a “panic situation inside the cabin” while another said “scores” of passengers suffered nose bleeds.

Panic situation due to technical fault in @jetairways 9W 0697 going from Mumbai to Jaipur. Flt return back to Mumbai after 45 mts. All passengers are safe including me. pic.twitter.com/lnOaFbcaps

— Darshak Hathi (@DarshakHathi) September 20, 2018

@jetairways Flight 9W 697 made an emergency landing back in Mumbai. Airplane lost pressure immediately after taking off…scores of passengers including me bleeding from nose….no staff to help…no announcement on board to wear the oxygen mask.passengersafety completelyignored pic.twitter.com/vO9O95aMCP

— Satish Nair (@satishnairk) September 20, 2018

NDTV reported that India’s Civil Aviation Minister, Suresh Prabhu, had ordered a safety audit of all scheduled airports, with the findings due within 30 days.

A Jet Airways spokesman said the flight’s cockpit crew had been “taken off scheduled duties pending investigations”.

Jet Airways statement on flight 9W 697 of 20th September 2018. pic.twitter.com/D99vyFFIv2

— Jet Airways (@jetairways) September 20, 2018

Questions have also been raised about whether the pilots might have a case of negligence to answer. They are supposed to apply the correct cabin air pressure settings before take-off as part of pre-flight checks.

Loss of cabin pressure is a serious emergency in an aircraft flying at cruising altitude. It reduces the flow of oxygen in the cabin and, in severe cases, can cause hypoxia.

Mumbai-based Jet Airways has 123 aircraft in operation and is India’s second-largest airline after Indigo.