Police and the ambulance service attended.
A statement from the police says: “We were contacted shortly before 4.30pm on Tuesday, 13 October with reports that people could be heard inside a lorry trailer on Ocean Boulevard, Stanford-le-Hope.
“Officers arrived and found four men and a teenage boy inside the trailer.
“The lorry driver, a 26-year-old man, has been arrested on suspicion of assisting unlawful immigration.
“He remains in police custody.”