Police forces across the UK carried out a coordinated crackdown on the illegal trade between May 13-20, seizing £312,649 in cash and 46 weapons — including a crossbow and an axe, Sky News reported.
The week-long operation, formulated by the National County Lines Coordination Centre, resulted in the arrests of 500 men and 86 women, with another 519 vulnerable adults and 364 children taken into safeguarding.
County lines gangs are notorious for grooming such people into becoming couriers who transport banned substances from towns and cities into more rural areas, with orders taken by phone.
The growth of county lines — which a Sky News investigation found was worth £3 million per day — contributed to the number of cases of modern slavery involving UK minors going from 676 in 2017 to 1,421 in 2018.
During the police operation — which uncovered £176,780 of cocaine, £36,550 of crack and £17,950 of heroin — 30 people were referred as potential victims of slavery or human trafficking.
Nikki Holland, who leads the response to county lines at the National Crime Agency (NCA), said, "Tackling county lines and the misery it causes is a national law enforcement priority and these results demonstrate the power of a whole-system response to a complex problem that we're seeing in every area of the UK.
"We know that criminal networks use high levels of violence, exploitation and abuse to ensure compliance from the vulnerable people they employ to do the day-to-day drug supply activity."
She added that while police were making good progress in the fight against county lines, forces all over the country needed assistance from other sectors working with people at risk of becoming involved in the trade.
Nurses, teachers, social workers and doctors have all been urged to keep watch for signs that young people they work with may have fallen prey to a county lines gang.
Youngsters who suddenly have new and unaffordable belongings, go missing a lot, have friendships with older people or have unexplained injuries are all said to be possible victims.
Iryna Pona, policy manager at The Children's Society, said, "Everyone, including professionals, needs to know how to spot the signs that something is wrong and accept that these young people are not troublemakers, but vulnerable children who are being groomed and need help."
The nationwide arrests came a week after three county lines drug dealers were jailed for a total of 12-and-a-half years for recruiting six teenagers to transport illegal drugs to coastal communities.
Glodi Wabelua, Dean Alford and Michael Karemera, all 25, were charged under the Modern Slavery Act and are thought to be the first to face such a charge for drugs offences.
They were among thousands of people involved in county lines networks in the UK, where there are thought to be around 2,000 gangs working to expand their drug networks.