Four Vietnamese nationals have been arrested in London after an investigation into alleged people smugglers advertising small-boat crossings of the Channel on Facebook. The joint UK-French investigation alleges the group shared posts aimed at the Vietnamese community and charged migrants thousands of pounds to make the crossing. Officers arrested a 23-year-old woman at an address in Croydon, south London, a 64-year-old man at an address in south-east London and a man, 34, in Leicester on Monday, the National Crime Agency (NCA) said. A 25-year-old man was also arrested at the Croydon address on a warrant issued by the French authorities. The older man is thought to have acted as a driver, collecting migrants who arrived on small boats and, at least once, taking them back to the Croydon address. The first three people were held on suspicion of assisting unlawful immigration and questioned by officers. All three were charged and appeared at Croydon magistrates court on Tuesday, the NCA said. The 25-year-old man will face extradition proceedings after he was allegedly involved in people smuggling and drug offences. A further 12 individuals suspected of being linked to the same people-smuggling network have been arrested in Paris. The home secretary, James Cleverly, said: “We are using every possible lever at our disposal to crack down on people smugglers and break their supply chains. “Just last week, we signed a new agreement with Vietnam, strengthening our cooperation on illegal migration. “Together with law enforcement agencies, such as the NCA, our French partners, and other countries like Vietnam, we are committed to dismantling the criminal gangs who are trying to turn a profit by abusing our borders.” Chris Farrimond, the NCA director of threat leadership, said Vietnamese nationals now made up a large number of people arriving on small boats. “We allege this group were advertising their crossing services on social media to encourage others from their country to make the same treacherous journey. “The NCA is continuing our work with partners and has had thousands of social media pages and posts advertising organised immigration crime services removed from platforms … our investigation continues to target people smugglers both in the UK and overseas at every step of the route.”