National crime squad officers seeking to smash a people smuggling ring have carried out raids in Hartlepool.
The National Crime Agency (NCA) says it is carrying out a 'major operation' in multiple locations.
Two of the raids were carried out in Hartlepool, with two arrests made.
Officers are targeting a group suspected of people smuggling in the North East, London and the South Coast.
The investigation has been going on for a year, according to the NCA, and more than 20 properties have been raised.
Officers say 21 arrests were made across the country, including the two in Hartlepool.
A statement from the National Crime Agency said: "The National Crime Agency (NCA) is carrying out a major operation targeting a suspected people smuggling organised criminal network in the North East, London and the South Coast.
"The operation is the latest phase of a year-long investigation, which has involved law enforcement colleagues in the UK and in Europe.
"More than 20 properties have been raided by NCA officers supported by Cleveland, Northumbria, Sussex and Metropolitan Police colleagues, and a number of arrests have been made.
"The operation is ongoing with searches taking place at several locations including Middlesbrough, Hartlepool, Stockton, Newcastle, Hastings and London."
Cleveland Police temporary superintendent Sharon Cooney said: “We are pleased to have been able to work alongside the NCA as part of a national operation around people smuggling.
“These crimes are not confined to our local towns and communities - they are national and international and require the highest level of response.
“We will continue to work with our communities and regional and national policing colleagues to ensure that people smuggling, the exploitation of the most vulnerable by the most ruthless, will not be accepted.”
The strike was one of the NCA’s biggest since it began operations in 2013, with about 350 officers from the agency and its partners taking part.
It followed an NCA investigation into a Kurdish network suspected of smuggling people to the UK from France, Belgium and the Netherlands.
Migrants are believed to have paid between £5,000 and £10,000 to be smuggled by the group.
The NCA worked closely with the French Police Aux Frontières (PAF), the Belgian Federal Police and Dutch Kmar in the year-long investigation which led up to the strike.
Agents linked to the network are alleged to have recruited drivers both on the Continent and in Teesside.
NCA deputy director Tom Dowdall said: “The number of officers deployed today by the National Crime Agency, the police and partner agencies reflects the scale and severity of the suspected criminality.
“It is one of the biggest operations of its kind undertaken by the NCA.
“We believe we have identified and disrupted a significant network which is suspected of smuggling hundreds of migrants into the UK and planned to carry on going.
“People smugglers don’t think twice about putting lives in danger, employing a range of dangerous methods as they attempt to evade border controls.
“It is a crime predicated on exploitation of vulnerable people and their treatment as a commodity instead of as human beings.
“If anyone in the local community thinks they have information about linked criminality in the area we’d urge them to call the local police.”