About $20 million in cash that was hidden inside a box spring in a Massachusetts apartment has been seized as part of a wide-ranging investigation into TelexFree, an internet telecom company that was actually a massive international pyramid scheme, federal prosecutors said.

The cash was found by investigators who had tailed a Brazilian man from New York. That man, Cleber Rene Rizerio Rocha, 28, was charged with conspiring to commit money laundering and was held after an appearance in federal court Thursday pending a detention hearing scheduled for next week.

TelexFree had few customers and made most of its revenue from people buying into the company with a promise of payouts for posting online ads for it, prosecutors have said. They were paid with money from new recruits, often friends and family of earlier investors. Although initially aimed at Brazilian immigrants to Massachusetts, authorities allege almost 1 million people worldwide were swindled out of nearly $1.8 billion.

TelexFree filed for bankruptcy in 2014, its assets frozen, and its two principals were indicted on federal charges of wire fraud and conspiracy. One of them, former chief executive James Merrill, pleaded guilty in October and awaits sentencing in February. The other, Carlos Wanzeler, fled to his native Brazil where he remains.