Indian Mango Pickle producing gas is that normal? I am trying to pickle some mangoes the Indian way. I boiled the jar in hot water, dried it and then added the mixture of spices, salt and mangoes to the jars after the mixture had cooled. I made the mixture in a frying pan to try and remove as much water as I could. After it was cooled, I put it in the jar and heated some mustard oil till it just barely started smoking. I let that cool and poured it over the mango spice mixture.

For the first three days it was fine. On the fourth day, I opened it to test the taste and ended up adding more salt. Now, there seems to be gas forming in the jar. I've noticed it a few times now. When I open the jar, I hear a whooshing noise as air escapes. It's quite a lot, since I opened the container about 3 times in a 10 hour period and each time gas escaped. Has this pickle gone bad? Or is this something that's normal?
This is completely normal and expected.

Indian pickle is fermented. One of the by products of that fermentation is gas.
The salt keeps undesirable bacteria from growing.

In the future you should use a container that can be less tightly closed and allow some of the gas to vent as it ferments. You wouldn't want a bottle to burst.