"The mine is not open to the public:" UWM officials seal openings at Neda mine after three boys rescued

DODGE COUNTY -- We are learning more about the Neda mine in Dodge County -- where three teenage boys were rescued Monday, July 11th after becoming lost inside the abandoned mine on Sunday afternoon. The University of Wisconsin-Milwaukee has owned the mine for about 40 years.

The Neda mine is an abandoned iron mine in Dodge County -- the site of the largest bat hibernaculum in the Midwest.

The property was acquired by the University of Wisconsin-Milwaukee in 1976.

At that time, an estimated 75,000 bats were using the mine.

Now, more recent estimates suggest that the population has grown to 150,000 to 200,000. The majority of these are little brown bats.

On Sunday, 16-year-old Tate Rose, 16-year-old Zachary Heron and 15-year-old Samuel Lein made their way into the mine.

Dodge County Sheriff Dale Schmidt said Monday a report that the boys were missing came in around 9:45 p.m. Sunday.

The boys' bicycles were located around 2:00 a.m. Monday near the mine.

Video shared by CNN Monday evening shows the moments after the boys were rescued from the abandoned mine Monday afternoon.

Sheriff Schmidt said the boys simply became curious, and entered the abandoned mine, where they got turned around and couldn't find their way out.

Workers once mined the land near the Neda mine for materials needed to help people get around.

"It was used mostly to build the rails of the railroads. The iron ore in the Neda mine is a low-quality iron ore. It`s not good for making steel, so they stopped mining here in the early 1900s, 1910-1915, something like that," Gretchen Meyer, UWM field station director said.

The Neda mine sat abandoned until UWM acquired it in 1976. Today, it is primarily used for bat research.

"It has very stable temperatures in the winter," Meyer said.

That's just what bats need -- about 50 degrees year round. The cold air at exhaust points collides with hot, summer air.

Dodge County Sheriff's officials said the three teenage boys on Sunday afternoon couldn't find their way out of the pitch black, chilly mine. Once they were in the mine, each of the boys' cell phones lost power -- so they were not able to call out of the mine.

"They were on the way from one place to another and decided they'd take a detour and do a little exploring -- went in a little father, got lost, turned around and as a result of not being able to find the entrance they went into, they slept in the mine overnight. I think, you get yourself into a situation, they did the smart thing and they did stay together. They didn't split up. They did get some rest and that was all key in what they did," Sheriff Schmidt said.

An exhaustive search would eventually include rescue crews from Madison and Milwaukee. It was a Milwaukee crew that found the boys just before noon.

"We kind of split off at a T intersection in the cave. One of our members went down one of the legs of the T and he could just barely hear one of the boys shouting out for help. They had one light with them and a BIC lighter and then those ran out. They were in the dark for an unknown amount of time. Their voices were very weak. We shined some lights on them. They were sitting there, obviously very happy to see the first rescuer," Brian McNulty with the Milwaukee Fire Department said.

Meyer says the unstable ground created a hole -- and that's how the boys got in.

That opening was sealed Tuesday, along with any others researchers found.

UWM workers toured the area surrounding the Neda mine Tuesday -- making sure any possible entrances were marked -- to ensure bats are the only ones occupying the mine.

"The mine is not open to the public. It`s posted. The entrances are closed and gated, and we don`t want people going in the mine," Meyer said.

The boys were said to be doing fine after their rescue. Their families asked for privacy.