Cathay Pacific will be adding inflight and post-landing checks on emergency equipment on board its aircraft, after it uncovered six instances of tampered portable oxygen bottles.

The carrier states that the six incidents occurred over a month, between August and September.

The latest took place on 16 September and involved one portable oxygen bottle, which had a shut-off valve “inadvertently” opened by cabin crew during a routine check. This led to the bottle to be found in a low-pressure state.

Three other instances also involved a single oxygen bottle, and were found on Cathay Dragon flights. The last two incidents occurred on the same flight, CX826 from Hong Kong to Toronto, a day apart. On 17 and 18 August, five and eight out of 22 portable oxygen bottles respectively were found to be in low pressure state.

Cathay states that the issues were uncovered during routine pre- and post-flight inspections.

Internal investigations into the matter are ongoing, says Cathay, and cabin crew from the flights involved have been suspended from duties. Some have since returned to work, while others are still assisting investigations.

The airline has also informed the Hong Kong Civil Aviation Department and the police. It stressed that passenger and crew safety were not compromised by the incident, and that the oxygen bottles were checked and recharged upon discovery.

Portable oxygen bottles are used to allow crew to move around the cabin during cabin depressurisation. Passengers, as well as cabin crew, have in-seat oxygen supply, and this was not affected by the spate of incidents.

Correction: An earlier version of the article misquoted information about passenger and crew safety. It has since been amended to reflect the correct statement.