1. The Mongolian gas distribution network experienced a rupture on April 1st, 2011, disrupting gas supply to parts of Ulaanbaatar.
2. Repair works were completed and gas supply was restored to most affected areas by April 20th, with the exception of the Selbe and Bayangol districts which saw full restoration by May 7th.
3. An investigation found the rupture was caused by deterioration of the cast iron pipes in the network due to their age and corrosion from soil and groundwater conditions. Upgrades to the network are ongoing to replace aging infrastructure and prevent future disruptions.