An Indian Army soldier went missing while anothersustained serious injuries on Thursday following an avalanche in the mountainous Lugnak La region of north Sikkim, officials said.The two personnel were part of a 17-member group which came under the avalanche, they said."A snow clearance party came under a sudden snow slide in north Sikkim. All soldiers have been evacuated safely but for one soldier who is still missing," a senior Army official said."One of the soldiers sustained serious injuries and is undergoing medical treatment. Intense search is underway to locate the missing soldier," he said.