At least 30 passengers on a Jet Airways flights from Mumbai to Jaipur on Thursday started bleeding from their nose and ears after the crew forgot to switch on the system to maintain cabin pressure, PTI reported. The Boeing 737 aircraft returned to Mumbai due to a “loss of cabin pressure”, according to a Jet Airways statement.

There were 166 passengers and five crew members on board the flight.

All the passengers were treated at the Mumbai airport, but five of them were taken to Dr Balabhai Nanavati Hospital for a medical check where doctors said they suffered from mild conductive deafness, PTI reported.

Chief Operating Officer of the hospital Rajendra Patankar said preliminary tests showed the five passengers suffered barotrauma of ear, which is caused due to a change in air pressure. Mild conductive deafness is a temporary condition which is likely to take a week or 10 days to heal. “They are advised not to fly till then,” Patankar said. They were later discharged as their health condition was stable and they did not need to be admitted, he said.

“The 9W 697 Mumbai-Jaipur flight was turned back to Mumbai after take off as during the climb crew forgot to select switch to maintain cabin pressure,” said Deputy Director General of DGCA Lalit Gupta, according to the Hindustan Times. “This resulted in the oxygen masks dropping. Thirty out of 166 passengers experienced nose and ear bleeding, some also complained of headache.”

The Aircraft Accident Investigation Bureau has initiated an investigation. “The flight’s cockpit crew has been taken off scheduled duties pending investigation,” an unidentified Jet Airways spokesperson told ANI.

An unnamed officer of the Aircraft Investigation Bureau said that one of the pilots is a captain with more than five years of experience, reported PTI. The officer added that the incident could be a case of negligence on the part of the pilots since controlling cabin pressure control is part of a check before operating a flight.

The Ministry of Civil Aviation has taken cognisance of the incident and directed the DGCA to file its report immediately, ANI reported.

The flight was re-scheduled to take off from Mumbai at 10.15 am, reported ANI.