A Yemeni army helicopter carshed today ” in mysterious circumstances ” in the southern Yemeni province of Shabwah, a Yemeni military source announced.  Four soldiers were wounded in the crash which occured near an oil pipeline in Oselan region in Shabwa province while attempting an emergency landing.An air force committee started investigation into the causes of the crash while helicpters headed to the scene of the incident to collect the ill-fated helicopter debris.