UPDATE: A404 crash that left two seriously injured 'may have happened after altercation involving another driver'

The A404 Amersham Road near Beamond End and Mop End is shut this afternoon amid reports of a serious crash. 

The busy A-road is closed both ways from Sheepcote Dell Road to Penn Street, according to traffic reports - and is expected to remain shut for a while. 

The incident supposedly involved two cars and the road was shut at around 4pm.

Bucks Fire and Rescue were called at around 3.30pm and had to release an injured woman from one of the cars involved. 

A man, girl and a boy were also injured but not trapped inside any of the vehicles. 

Firefighters had to use a special kit to contain a fuel and oil spill. 

More as we get it.