The accident occurred near the centre of the town of Sandefjord in the county on Friday morning, reports TV2.
“We received reports of the accident at 10:47 this morning. The trailer came loose from the car and three cyclists were injured,” operation leader Cathrine Klæstad of the Southeast (Sør-Øst) Police District told Nettavisen.
The three injured cyclists are men in their 40s and 50s and two have been flown to Ullevål Hospital with head and chest injuries.
The third casualty suffered broken bones and has also been taken to hospital, police confirmed via Twitter.
Skadeomfang: to menn i hhv. 40- og 50-årene er med luftamb. kjørt Ullevål. Skader i bryst og hode. Mann 50-årene har bruddskader, kjørt SIV.— Politiet Vestfold (@PolitiVestfold) August 4, 2017
“We have been in contact with Ullevål, who have said that the two are in a critical condition,” Klæstad told NTB.
Police technical staff were despatched to the accident scene along with emergency services.
The driver of the car from which the trailer came loose was a man in his 60s, according to Nettavisen's report. Police wrote on Twitter that the man's driving licence had been confiscated and that he was being monitored by a crisis help team attached to the local municipality.
The road was closed in both directions following the accident and two people were given emergency treatment inside ambulances at the scene, while all three cyclists were conscious immediately following the accident, reports local media Sandefjords Blad.
Police later wrote on Twitter that the road had been reopened, while also commending passers-by for delivering first aid and responding quickly in the immediate aftermath of the accident.
Veien er igjen åpent for normal ferdsel.— Politiet Vestfold (@PolitiVestfold) August 4, 2017