Canning tomato sauce problem, jar broken in boiling method
Jars burst either because of internal pressure or thermal shock.

There are a couple things you can do to reduce the risk of bursting.


use actual canning jars.
Some people like to reuse regular jars that aren't as strong. This will often work fine but increases the risk of bursting.
make sure the jar is hot.
A cold jar into hot water or a hot jar into cold water will burst almost every time.
bring water to a boil after adding jars
don't overtighten lids.
Rings should be tightened just enough to firmly hold the lid on. Too much and pressure won't be able to escape during boiling. Remember the bottle is sealed by pressure-not by the ring.


Based on your description, if you had any of these problems I would suspect the last.
However, sometimes bottles just burst because of manufacturing defects. This doesn't happen often but it is sad when it does.