The exact cause is unknown. But in a recent study, an experimental drug showed signs of halting the disorder in laboratory mice.

VOA: special.2010.05.19

Not only did the always interesting Lady Gaga show up inside a large egg-like structure, but unknown artists also won top prizes.

VOA: special.2011.02.18

Then on April thirtieth, two thousand seven,a huge fire of unknown cause almost completely destroyed South Hall.

VOA: special.2009.08.21

Their ancient languages contain a great deal of information about environmental systems and species of plants and animals that are unknown to scientists.

VOA: special.2009.12.02

They gave a name to this mysterious continent: Terra Australis Incognita, or the "Unknown Southern Land."

VOA: special.2009.06.03

If hoarseness continues or the cause is unknown, doctors should perform an examination called a laryngoscopy.

VOA: special.2009.09.02

This intense heat they project in a parallel beam against any object they choose, by means of a polished parabolic mirror of unknown composition, much as the mirror of a lighthouse projects a beam of light.

VOA: special.2010.09.01

"It's also trying to overcome the fear of cholera, because it's a new disease and it's unknown and it strikes quickly,".

VOA: standard.2009.09.14

The plan follows months of deadlock over Iran's nuclear program and the recent discovery of a previously unknown nuclear-enrichment plant near the Iranian city of Qom.

VOA: standard.2009.10.19

While the exact reasons are unknown, a diet of foods that quickly release sugar into the bloodstream is associated with a greater risk of Type 2 diabetes.

VOA: standard.2010.06.25

After a stop to lay a wreath at Russia's Tomb of the Unknown Soldier, Mr.Obama will head to the Kremlin for a private meeting with Russian President Dmitri Medvedev.

VOA: standard.2009.07.06

(Choral music) On a cold and gray morning, German Chancellor Angela Merkel and French President Nicolas Sarkozy together rekindled a flame before the Tomb of the Unknown Soldier near the Champs Elysees.

VOA: standard.2009.11.11

On Memorial Day,the day Americans remember the fallen, the president or vice president traditionally lays a wreath at the Tomb of the Unknown - this is the scene from last year.

VOA: standard.2010.05.26

Afghan and NATO officials say that Taliban insurgents in the northern Kunduz province were driving two hijacked fuel trucks to an unknown destination when fighter planes located them on a river bank and bombed them.

VOA: standard.2009.09.04