Conspiracy theories about the purported dangers of 5G wireless networks have prompted anti-5G activists to set June 6 as a global protest day against the spread of the new technology. The activists warn that 5G radio emissions are harmful to human health, a charge not supported by most scientists.

The trade group for companies that install wireless equipment on towers, known as NATE: The Communications Infrastructure Contractors Association, issued a warning to its members this week about the protest day.

“NATE member companies set themselves apart by embodying the characteristics of work ethic, professionalism, safety, and quality on a daily basis,” the group wrote. “NATE reminds our member companies and their employees to remain safe, exercise vigilance, and report any unusual or suspicious activities that they witness when traveling to and working at tower sites this weekend.”

The unsupported health theories have already led to vandalism and burning of some 5G equipment, particularly in the United Kingdom. Telecommunications industry groups fear that the protest day could lead to more widespread damage in the United States.

The wireless industry is spending tens of billions of dollars to upgrade its current 4G LTE networks to 5G, which offers connection speeds 10 to 100 times as fast and enables new applications like mobile high-resolution virtual reality. But 2020 has been a difficult year for 5G, as unfounded health fears have stalled the network upgrades necessary to reach faster speeds in some cities, while the coronavirus pandemic has slowed sales of 5G-compatible phones.

More must-read tech coverage from Fortune:

• Why GitLab hired a “head of remote” before the coronavirus pandemic
• Everything to know about rubber bullets and their risks
• Why Zoom is leaving its free videoconferencing with weaker encryption
• Walmart pushes forward with new HQ plans to help staff collaborate post-pandemic
• WATCH: Zoom’s ups and downs since the coronavirus crisis