A bus carrying 41 passengers caught light as it travelled south along the A2 near São Bartolomeu de Messines on Saturday afternoon.
The bus operated by Transol, carrying only Portuguese passengers who were enjoying a coach tour, was burnt out but everyone managed to exit the vehicle before the flames consumed the interior.
The Messines bombeiros are located close by and reacted swiftly, with GNR officers in attendance, after the alert was phoned in at around 17:00hrs.
The A2 was blocked off but reopened after about half with a relief bus collecting the passengers.
The GNR will investigate the case but an electrical fault is thought to have been the cause.
