Pocar and del Ponte were speaking at a news conference in The Hague on Sunday.
The president of the ICTY said that the coroner was unable to establish the cause of death on Saturday and that Dutch and Serbian pathologists would carry out an autopsy today.
Del Ponte said an autopsy usually lasted 4-5 hours while toxicology tests took 24 hours to complete so the first results could be expected on Sunday evening and Monday morning, while other details would be known next week.
The tribunal's Registry requested a full report on the investigation that is being conducted by the Dutch authorities as soon as possible, Pocar said.
He said the trial chamber which had been conducting the Milosevic trial for more than four years would deal with the status of the proceedings in the foreseeable time.
Under the tribunal's rules of procedure, the trial chamber will issue an order to discontinue the trial due to the death of the accused.
The prosecution has introduced almost 300 witnesses and 5,000 pieces of evidence, and after the first stage of the trial in 2004, the trial chamber did not drop any of the 66 counts of the indictment, del Ponte said.
After 446 days of the trial, which started on 12 February 2002, only 50 business hours were left and the trial should have been completed by the end of spring, del Ponte said.
It's a pitty for justice that the trial will not be completed and a verdict passed. However, other high-ranking officials too have been indicted for the same crimes as Milosevic, del Ponte said, adding that the trials of eight men indicted for war crimes in Srebrenica and six former Serbian leaders indicted for Kosovo would start by the end of the year.
She recalled that the two most wanted fugitives from the tribunal were still at large.
Now more than ever I expect Serbia to finally arrest Radovan Karadzic and Ratko Mladic and transfer them to The Hague as soon as possible, del Ponte said.
On the occasion of the third anniversary of the death of Serbian prime minister Zoran Djindjic, who was assassinated on 12 March 2003, del Ponte praised his courage to hand Milosevic over to the tribunal.
Answering critical questions by reporters who wanted to know if the trial could have been shorter had the indictment been more concise and focused only on the gravest crimes, del Ponte said this was not only an issue of the indictement and the verdict, because facts had to be established so that the victims could know what happened.
Asked if she ruled out the possibility that Milosevic committed suicide by mixing medications or in some other way, del Ponte said this was not ruled out because there had already been cases of suicide in the tribunal's detention unit, but that one should wait for the autopsy results.
She dismissed allegations about Milosevic having been poisoned as rumours.