It happened at around 00:30 on Sunday morning.
All emergency services were called to the scene, including a double crewed ambulance. Given the potential number of casualties, a second paramedic ambulance and an incident officer were dispatched a short time later.
Two of the people involved had to be taken to the Emergency Department for further treatment. Ambulance clinicians assessed another three people at the scene, however none of these needed further medical attention.
Guernsey Police, Guernsey Fire & Rescue Service and Civil Protection were also in attendance. The road remained closed after the Ambulance and Fire services left the scene, as police officers spent hours investigating the crash site.
Forest Road was reopened at around 04:50 this morning.