The raids by the National Crime Agency (NCA) targeted an organised crime group, which authorities said was linked to the prolific smuggling of migrants to the UK by lorry.
GB News has been told the arrests relate to two separate events in 2019, where a total of 32 migrants were found in the back of HGVs in the Netherlands and France.
Both drivers and another facilitator were later jailed in those countries.
NCA investigators said members of the crime group were also suspected of involvement in arranging for lorries to be broken into, and people were loaded on board without the knowledge of drivers.
Raids by the NCA targeted an organised crime group
NCA
Tracker devices were found attached to the vehicles, which allowed the people smugglers to locate the lorries.
Authorities say migrants were then placed in the rear, as the HGVs continued their journey to the UK.
Group members are also suspected of obtaining a boat as part of their plans to bring migrants to the UK over the English Channel.
This morning, a 39-year-old man was arrested in Dagenham, east London, on suspicion of conspiring to facilitate illegal immigration.
He is alleged to be a senior member of the conspiracy.
In series of co-ordinated raids, a 37-year-old man was arrested in Ilford, and two other men, a 36-year-old, and another aged 42 were detained at properties in Streatham and Leytonstone.
All of those detained, were arrested on suspicion of facilitation of illegal immigration.
Today's raids are the second major operation in a week
NCA
All are due to be questioned by National Crime Agency officers.
NCA Branch Commander Andy Noyes said: "This operation has targeted those who we suspect are key members of a people smuggling crime group.
"Organised immigration crime is a chronic and dangerous threat and the smugglers pay no regard to the lives of the people they attempt to transport, whether that be by boat or in vehicles.
"While putting people in lorries might make the issue less visible to the public, it is no less dangerous to those being smuggled, and unfortunately we have seen the tragic consequences this can have."
In October 2019, the bodies of 39 Vietnamese nationals were found in the back of a refrigerated lorry in Grays, Essex.
Post Mortems revealed the group suffocated inside the sealed trailer.
Today's raids are the second major operation in a week the NCA has mounted, targeting suspected people smugglers.
Last Tuesday, law enforcement officers in the UK, France, Germany and the Netherlands arrested 39 alleged members of an organised criminal gang believed to responsible for smuggling 10,000 people into the UK in recent months.