Four people have been charged after an investigation into suspected illegal immigration and cannabis production, Lancashire Police have said.

They are charged with conspiracy to produce cannabis, four counts of assisting in unlawful immigration, and possession of a false identification document with improper intention.

Six people were arrested after dawn raids in Blackburn, Bolton and Darwen yesterday.

Nicknamed "Operation Canvas", the investigation looked at the alleged employment of Vietnamese nationals, believed to have entered the country illegally.

Searches also took place at nail bars in Blackburn and Bolton, where it is believed some people may have been working.

Two people have previously been arrested and charged in connection with Op Canvas.