Singapore Airlines will be offering a refund to passengers of SQ317 which had to make an emergency landing in Azerbaijan on Sunday.

The root cause of the problem that forced the plane to make the landing is currently being investigated, said the airline in a statement.

The airlines said it was focusing on a door on the main deck that appears to have suffered a leak, leading to the change in cabin pressure.

This door will be removed and examined thoroughly by SIA and specialists from airplane maker Airbus, said SIA in a statement. A replacement door will be fitted to the aircraft in Baku, the capital city of Azerbaijan, before it returns to Singapore for a more thorough inspection, it added.