Serious Incident involving Bombardier DHC-8-Q400 aircraft, 5N-BPU

Accident Investigation Bureau (AIB) was not officially notified of the serious incident but got to know about it through social media on 19th April, 2017. AIB investigators were immediately dispatched to the Aero Contractors’ hangar in Lagos, where the aircraft was parked.
On the 18th of April, 2017 at about 17:50 h, a Bombardier DHC-8-Q400 aircraft with registration marks 5N-BPU, operated by Aero Contractors Company of Nigeria Ltd as a scheduled flight NIG316, while cruising at FL240, 80 NM inbound Lagos from Port Harcourt, experienced bluish smoke which gradually increased in density within the cabin.
The smoke progressed into the cockpit. The lavatory smoke detector aural warning activated, and the AFT BAGGAGE light illuminated on the Fire Panel but there was no burning smell perceived. At 17:55 h the crew donned Oxygen masks and requested clearance to descend. NIG316 was cleared for immediate descent to 2,200 ft AMSL and requested to contact Lagos Approach. The aircraft contacted Lagos Approach requesting fire assistance on the ground.
The crew followed the FUSELAGE FIRE, SMOKE or FUMES in the QRH and executed “SMOKE” (Warning Light) checklist procedure, the aircraft landed safely on runway 18L at about 18:03 h and taxied to Aero Contractors maintenance facility at the General Aviation Terminal (GAT).
The passengers disembarked normally without injuries.