The younger brother of absconding prime conspirator Tiger Memon, Yusuf Memon was convicted for the terror strikes and was serving a life sentence.
The exact cause of the death is not yet clear and his body has been sent for an autopsy to a Dhule hospital, said an official.
Among other things, Yusuf Memon was found guilty of allowing the use of his premises in Mumbai for terror activities to Tiger Memon, who allegedly masterminded the attacks along with the fugitive mafia don Dawood Ibrahim Kaskar and others.
Incidentally, another of their brothers - Yakub Memon who was convicted and awarded a death penalty in the same case - was hanged in 2015 at the Nagpur Central Jail.
At least 315 persons were killed when 12 strategically bombs exploded in quick succession at various strategic locations like hotels, the BSE, the gold jewellery hub of Zaveri Bazar, Regional Passport Office, Shiv Sena Bhavan and other sites, on March 12, 1993, considered among the biggest terror acts globally.