The world’s longest cave just keeps getting longer.

Mammoth Cave National Park announced Thursday that six additional miles have been added to its cave system, tallying to a total length of 426 miles.

The announcement came during the 50th anniversary of the cave connection that first crowned Mammoth Cave as the longest cave, then at only 144.4 miles.

“It is very fitting that we can now announce the new miles during our anniversary events celebrating years of great work accomplished by the Cave Research Foundation,” Mammoth Cave Superintendent Barclay Trimble said in a news release. “Our teams have come together to mark this important milestone and we hope the community will take advantage of some special opportunities to learn more about the CRF and even be able to speak directly to the history makers themselves.”

The six extra miles aren’t in one big chunk or isolated to one area of the cave, according to Molly Schroer, Mammoth Cave public information officer.

“These are in small, hundred-foot segments,” she said. “It adds up.”

Schroer isn’t sure if the rate of discovery has been increasing lately but said that CRF has been very active recently in going down into the cave to survey and update maps, which often leads to new findings.

Roger Brucker, one of the CRF’s key pre-connection explorers and author of several caving books, said many people think Mammoth Cave will surpass the 500-mile mark relatively soon. He’s predicted that by the end of the century, he could see it extending as far as 1,000 miles.

“We don’t have any time frame for when we’re trying to find the end,” Schroer said.

Mammoth Cave is far ahead of its peers.

The second-longest cave, Sistema Sac Actun, is 234 miles long, according to data compiled by Caverbob.com. The third-longest cave, Jewel Cave in Custer, S.D., is 212 miles. The fourth-longest is Sistema Ox Bel Ha at 197 miles.

Sistema Sac Actun and Sistema Ox Bel Ha are underwater caves located on either side of the city of Tulum on Mexico’s Yucatán Peninsula.

At a combined 431 miles currently, if they were ever to connect, they could give Mammoth Cave a run for its money, according to Chris Groves, WKU hydrology professor.

Schroer said Mammoth Cave researchers collaborate across the world in their research, but they do have somewhat of a “friendly rivalry with Mexico.”

“We like to hold that title,” she said.

Mammoth Cave is holding several events through Sunday to celebrate the connection’s 50th anniversary.

On Friday night, the surviving members of the 1972 CRF discovery team – Richard Zoph, Steve Wells, Cleve Pinnix, Gary Eller and Pat Wilcox – will have a free fireside chat open to the public in the park’s amphitheater to discuss their experiences.

– To see the full list of events, visit www.nps.gov/maca/planyourvisit/1972- connection-event.htm.

– Follow regional reporter Sarah Michels on Twitter @sarah_michels13 or visit bgdailynews.com.