Cool Oak Lane, between Hendon and Kingsbury, is currently flooded with emergency services.
The Brent & Kilburn Times can see dozens of vehicles, including police, fire and the London Ambulance Service.
Emergency crews are currently searching near the water.
A raft is also being prepared to enter the water area.
Cars are being diverted away from the bridge by the reservoir.
The Metropolitan Police, London Ambulance Service and London Fire Brigade have been contacted.
