Taliban defence minister "died in Karachi gaol"

The Taliban yesterday confirmed that its former defence minister during the Islamic Emirate had died nearly two years ago in a Pakistani prison. Their website says that he was detained on 3 January 2007 by the Pakistani government in Balochistan, but that little was heard from him after that. Only in the last few days did his family receive news from Pakistan that he died in prison in Karachi due to "heart complications" on 5 March 2010.
In a statement the Taliban says: "The Islamic Emirate of Afghanistan considers the martyrdom of Shaheed Mullah Obaidullah Akhond a void for the entire Islamic Ummah and especially Afghanistan which cannot be compensated and vigorously demand from the Pakistani officials to give the complete and factual information of Al Haaj Mullah Obaidullah’s detention, illness and death to the Islamic Emirate. In this regard, we also hold the International Red Cross responsible as the news of the martyrdom of Al Haaj Mullah Obaidullah Akhond was received after a period of 2 years and also for not providing any type information about the concerned martyr and others to the families of these prisoners of Islamic Emirate who are held in Pakistan and we also demand that they fill this shortcoming in the future as it is their obligation."
It is clear from the statement that the Taliban itself was in ignorance of the fate of Mullah Obaidullah. He had recently been slated as a potential member of a negotiating team with the Karzai regime and his release by Pakistan was one of the preconditions the Taliban insisted upon before they would agree to negotiations. They are now demanding an inquiry into his death.
His death will come as a shock to many Taliban members. As one of the most senior Taliban figures and someone known to be very close to Mullah Omar, the intriguing question is whether or not Mullah Obaidullah was murdered under torture or died of natural causes in captivity. 
Was he seen by the Pakistanis as one of the old guard around Mullah Omar, whose outlook did not suit Pakistani interests any longer? Although he was one of those who began to reorganise the Taliban once it had fled into exile in Pakistan, it is possible that he favoured negotiations to end the conflict. He was close to Mullah Barodar, who was also arrested by the Pakistanis, some say because Barodar was also in favour of negotiations with the Karzai regime. If his death was natural why was it covered up by the Pakistanis for so long? Any more information would be appreciated.