(CNN) Online romance scammers are busy stealing money and hearts across the United States.

Just this week, federal officials announced that they charged 80 people -- including Nigerians based in Los Angeles -- in businesses and romance scams worldwide.

The Federal Trade Commission has warned that scams that prey on vulnerable people cost Americans more money than any other fraud reported to the agency last year. More than 21,000 people were conned into sending $143 million in such schemes in 2018 alone, it reported.

And that number has skyrocketed in recent years, with losses that are almost quadruple 2015 figures.

"Reports indicate the scammers are active on dating apps, but also on social media sites that aren't generally used for dating. For example, many people say the scam started with a Facebook message," the FTC says.

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