Four people have been transported to hospital following a serious crash in Royalla this afternoon.

Just before 1pm, ACT and NSW Emergency services responded to reports of a two-vehicle crash on Old Cooma Road.

One of the vehicles had caught fire but was quickly extinguished by Police.

A pregnant female, male and child from the Toyota Hilux were all treated by NSW Ambulance paramedics and transported to hospital in a stable condition.

Firefighters from Fire and Rescue NSW worked for more than an hour to release a 19 year-old male trapped in the Hyundai Tucson before he was taken to hospital with serious injuries.

Old Cooma road was closed for most of the afternoon until the scene was cleared.

Officers attached to Monaro Police District have commenced an investigation into the crash.