A cooking gas cylinder exploded accidentally in Shiv Shakti langar in Baltal base camp, police said.
"The explosion resulted in death of four relatives of sewadars (volunteers) at the langar," a police officer told IANS here.
Langars are the free community kitchens set up by various religious organisations to serve food to all the visitors for free.
So far, over three lakh pilgrims have participated in the yatra which started June 28. The yatra will end on Aug 10.