The M11 near Harlow was closed between junctions eight and nine as officers attended the scene.
The police were called shortly before 6pm on Wednesday.
The 14 people in the back were detained after being checked by the ambulance service, police said.
The 30-year-old driver and a passenger were arrested on suspicion of facilitating illegal entry, the force added.
Highways England placed closures in both directions following a request from Essex police.
Hundreds of drivers were trapped following the illegal activity.
A source then revealed that the officers then called in paramedics and a HART team to check the suspected immigrants.
The group were given water and medical treatment, and it is unclear how long they remained in the lorry’s trailer.
Witness Andy Brookes continued: “The police closed the road just before my vehicle, then loads more turned up.”
The 44-year-old from Earls Barton continued: “I saw at least four people in the back of the trailer that were wearing COVID face masks, and I saw about six or seven people on the grass at the side of the motorway.”