Dig for ancient pyramid in Bosnia

On Friday, a team of rescue workers from a local coal mine, followed by archaeologists and geologists examined the tunnel, thought to be 2.4 miles (3.8km) long.

The team found two intersections with other tunnels leading off to the left and right.

Their conclusion was that it had to be man-made.

"This is definitely not a natural formation," said geologist Nadja Nukic.