Some attendees of the Bitcoin 2021 event in Miami have tested positive for COVID-19 after returning home from the conference, leading to a wave of negative media coverage and social media speculation it could turn into a “super spreader event.”

Bloomberg called Miami Bitcoin a “Covid hot spot” while Gizmodo reported the conference “may be the latest COVID-19 super spreader event.”

Arcane Research chief investment officer Eric Wall was among those to contract the virus, tweeting on Thursday that he underwent a CT scan after suffering from a “high fever” and “chest pains,” with medical staff having suspected he may have a blood clot in his lungs. No blood clot was found, and Wall was discharged from the hospital and returned home.

Luke Martin of automated trading software developer Coinist also admitted to testing positive for COVID-19.

According to CNBC, at least 12,000 people attended the event, which did not require proof of vaccination or enforce a mask mandate. The event lasted for three days at Miami’s Mana Wynwood convention center, cramming into crowded auditoriums while social distancing was not enforced.

The event was Miami’s first major conference since the beginning of the pandemic. According to a New York Times report, lines to enter the building “stretched for more than a mile.”

Miami mayor and Bitcoin proponent Francis Suarez spoke at the event and was introduced on-stage as “probably the most irresponsible politician in all of America” and “the mayor of the meccas of freedom.”

Social media reports have estimated the number of attendees and positive tests may be higher than mainstream reports. Influencer Mr. Whale told his roughly 235,000 Twitter followers that “dozens” of conference-goers have since tested positive, estimating the event could have seen more than 50,000 attendees.

Related: The female speakers who made an impact at Bitcoin 2021 in Miami

A screenshot of an image retweeted by Bitcoin 2021 organizer Dylan LeClair that scathingly dismissed the United States Centers for Disease Control and Prevention’s COVID-19 Vaccination Record Card system has circulated on social media.

Bitcoin 2021 was not the first crypto conference to have COVID-19 transmissions, with Torus Labs co-founder and CEO Zhen Yu Yong urging attendees of the Ethereum Community Conference in Paris and ETHLondonUK Hackathon in early 2020 to get tested when he was diagnosed with the coronavirus after participating in the events.