What was the Ghazi Attack in Indian subcontinent?

Ghazi was a war submarine in the Pakistan Navy. The submarine was a flagship Submarine for Pakistan. It was loaned by the US Navy. In the 1971 war in the Indian Subcontinent, the Ghazi submarine sank due to various unknown circumstances. The Pakistan navy had deployed a number of underwater mines in the region. It may have been an attack by the Indian Navy and/or may have been one of the mines they had placed themselves. It's unclear what exactly happened, but the Indian Navy destroyed all records of their investigations in 2010.