Salt Lake City Public Lands Department photo.

Strange antennas have appeared in the foothills around Salt Lake City and authorities have no idea what they are or who put them up.

As first reported by KSLTV 5 in Utah, people first began noticing the antennas a year ago. They're simple machines made up of a LoRa fiberglass antenna, a locked battery pack, and a solar panel to power it. The Salt Lake City public lands department has been pulling them down as they find them, and told KSLTV that there have been as many as a dozen.

It's illegal to place structures on public lands without permission and some of the antennas have appeared on steep peaks. In one instance, the removal of an antenna required a team of five people. Other antennas were found on land managed by the University of Utah and the Forest Service.

Tyler Fonarow, Salt Lake City's recreational trails manager, told Motherboard that when the antennas were first noticed a year ago, "We didn't really have the bandwidth to look into it or remove them," he said.

Fonarow said that there were no identifying marks on the antennas and that they'd been bolted into the stone and required special tools to remove. "We honestly didn't even open the box," he said. "We just wanted it off the hill."

"Our Trails team and Foothills rangers have found some unauthorized solar panel towers in the Foothills," Salt Lake City Public Lands said in a post on Facebook. "If you have information about these towers or who they belong to, please call our office at (801) 972-7800 so we can return them back to their owner."

Fonarow told Motherboard that they'd pulled two of the antennas down and are aware of a few more, but that the winter weather makes it hard to identify and remove them. "It's not a high priority for us," he said. "We'll get to it when we get to it."

According to Fonarow, the highest elevation one of the antennas had been found at is the top of Mount Wire, which is more than 7,000 feet. He said the trip out the mountain would take about an hour, but it would be a hard hike.

"One person could do it," he said. "But it would take two trips unless they're really strong. The three main components are a suitcase sized…plastic, weatherproof case for their electric equipment for the battery and router. It was about 50 or 60 pounds. And then there's two antennas, four to six feet, and the solar panel which is about three by four feet. It would be a pretty tough thing to do by yourself."

The router made Fonarow initially think the thing was a cell phone booster, he said. Another leading theory online is that the antennas are part of a cryptocurrency mining operation.

Helium is a type of cryptocurrency that uses antennas to create a long-range, wide-area network. Instead of proof-of-work releasing token rewards, Helium relies on what it calls proof-of-coverage. The wider the network, the more Helium you're mining. Helium mining requires the exact kind of antenna shown in the photos of the devices recovered by Salt Lake City authorities. There are plenty of articles online instructing people how to create solar-powered rigs for Helium miners to deploy in rural areas, and Helium miners are fond of bragging about the elevation of their antennas.