An ambulance has arrived at the scene after police swarmed on woodland near the lake on Watermead in Aylesbury after local reports that a dog walker has gone missing.
Thames Valley Police officers gathered around a car in the village square car park at around 5.30pm.
Officers carried out searches of the surrounding area and more police cars and vans joined the search later.
At around 8pm officers rushed to the far end of the lake to a wooded area near a popular commemorative bench and gathered by the bank of the lake.
One resident who claimed to have spoken to officers said they were concerned for the whereabouts of a dog walker who regularly visits the area.
Around 12 officers were at the scene with some seen carrying out searches in other areas of woodland around the village.
An ambulance met with police officers off a cul-de-sac towards the end of Ayleswater where the footpath which stretches around the lake begins.
No cordon has been put in place at the time of writing.
The picturesque Watermead off the Buckingham Road is hugely popular with dog walkers and runners.
More on this as it develops.