Britain's National Crime Agency says human trafficking and modern slavery are much more prevalent than previously thought, and there are 300 active police investigations across the U.K.

Agency official Will Kerr says investigators have found widespread evidence of people as young as 12 being sold for sexual exploitation or forced labor. He said victims can be found working in car washes, on construction sites, in brothels and at cannabis factories.

Kerr told reporters Thursday that "the growing body of evidence we are collecting points to the scale being far larger than anyone previously thought."

The agency is launching a campaign to raise public awareness of modern slavery. Kerr says signs of slavery include visible injuries, a distressed appearance and any indication an individual is being controlled by another person.