CAIRO (AP) -- How do you count almost 40 million handwritten paper ballots in a matter of hours and declare a winner? That's a key question in Iran's disputed presidential election. International polling experts and Iran analysts said the speed of the vote count, coupled with a lack of detailed election data normally released by officials, was fueling suspicion around President Mahmoud Ahmadinejad's landslide victory.
Iran's supreme leader endorsed the hard-line president's re-election the morning after Friday's vote, calling it a "divine assessment" and appearing to close the door on challenges from Iran's reformist camp. But on Monday, after two days of rioting in the streets, he ordered an investigation into the allegations of fraud.
Mir Hossein Mousavi, Ahmadinejad's reformist challenger, claims he was robbed of the presidency and has called for the results to be canceled.
Mousavi's newspaper, Kalemeh Sabz, or the Green Word, reported on its Web site that more than 10 million votes were missing national identification numbers similar to U.S. Social Security numbers, which make the votes "untraceable." It did not say how it knew that information.
Mousavi said some polling stations closed early with voters still in line, and he charged that representatives of his campaign were expelled from polling centers even though each candidate was allowed one observer at each location. He has not provided evidence to support the accusations.
His supporters have reported intimidation by security forces who maintained a strong presence around polling stations.
Observers who questioned the vote said that at each stage of the counting, results released by the Interior Ministry showed Ahmadinejad ahead of Mousavi by about a 2-1 margin.
That could be unusual, polling experts noted, because results reported first from Iran's cities would likely reflect a different ratio from those reported later from the countryside, where the populist Ahmadinejad has more support among the poor.
Mousavi said the results also may have been affected by a shortage of ballot papers in the provinces of Fars and East Azerbaijan, where he had been expected to do well because he is among the country's Azeri minority. He said the shortage was despite the fact that officials had 17 million extra ballots ready.
Interior Ministry results show that Ahmadinejad won in East Azerbaijan.
The final tally was 62.6 percent of the vote for Ahmadinejad and 33.75 for Mousavi - a landslide victory in a race that was perceived to be much closer. Such a huge margin also went against the expectation that a high turnout - a record 85 percent of Iran's 46.2 million eligible voters - would boost Mousavi, whose campaign energized young people to vote. About a third of the eligible voters were under 30.
Ahmadinejad, who has significant support among the poor and in the countryside, said Sunday that the vote was "real and free" and insisted the results were fair and legitimate.
"Personally, I think that it is entirely possible that Ahmadinejad received more than 50 percent of the vote," said Konstantin Kosten, an expert on Iran with the Berlin-based German Council of Foreign Relations who spent a year from 2005-06 in Iran.
Still, he said, "there must be an examination of the allegations of irregularities, as the German government has called for."
But Iran's electoral system lacks the transparency needed to ensure a fair election, observers said. International monitors are barred from observing Iranian elections and there are no clear mechanisms to accredit domestic observers, said Michael Meyer-Resende, coordinator of the Berlin-based Democracy Reporting International, which tracked developments in the Iranian vote from outside the country.
He noted that the election was organized and overseen by two institutions that are not independent, the government's Interior Ministry and the Guardian Council, a 12-member body made up of clerics and experts in Islamic law who are closely allied to the supreme leader Ayatollah Ali Khamenei.
Meyer-Resende said that to be sure of the results announced by the Interior Ministry, it must release data all the way down to the level of each polling station.
One of the central questions was how 39.2 million paper ballots could be counted by hand and final results announced by authorities in Tehran in just over 12 hours. Past elections took at least twice as long.
A new computerized system might have helped speed the process in urban centers, where most Iranians live, though it is unclear if that system was extended to every small town and village. And each ballot - on which a candidate's name was written in - would still have to be counted by hand before any data could be entered into a computer, aggregated and transmitted to the Interior Ministry in Tehran.
"I wouldn't say it's completely impossible," Meyer-Resende said. "In the case of Iran, of course, you wonder with logistical challenges whether they could do it so fast."
Susan Hyde, an assistant political science professor at Yale University who has taken part in election monitoring missions in developing countries for the Carter Center, agreed that would be uncharacteristically fast.
"If they're still using hand counting, that would be very speedy, unusually speedy," she said.
The Interior Ministry released results from a first batch of 5 million votes just an hour and a half after polling stations closed.
Over the next four hours, it released vote totals almost hourly in huge chunks of about 5 million votes - plowing through more than half of all ballots cast.
Arshin Adib-Moghaddam, a professor of Middle East politics at the University of London's School of Oriental and African Studies, said a major rigging process would require the involvement of powerful advisory bodies, including those in which one of the other candidates and a key Mousavi backer are prominent figures.
"Given that Mohsen Rezaei, one of the other presidential candidates, is the head of the powerful Expediency Council, for instance, it is highly unlikely that he wouldn't have received any information of such a strategic plan to hijack the election," Adib-Moghaddam said.