The accident happened on Sunday afternoon at around 1.40pm. The victims are two women and two men aged between 25 and 35.
Further south, an 80-year-old man died over the weekend in Santa Barbara de Nexe in Loulé in the Algarve after crashing the motorbike he was riding.
According to GNR police the accident happened at around 2.30pm in Ameixeira. GNR officers are investigating the circumstances in which the crash occurred.
In Évora, in the Alentejo, a man died this week and two others were injured, one of them seriously, following a work accident at Évora University.
The accident is said to have happened while the men were manoeuvring a crane. A source from the local rescue operations centre said ten fire-fighters and emergency medics were dispatched to the scene to help.