The lawmaker heading the inquiry into the disfiguring dioxin poisoning of opposition presidential candidate Viktor Yushchenko (search) has cast doubt on whether deliberate poisoning could be proven, as speculation mounts over who the culprit was.

Ukraine's (search) outgoing government on Monday sought to take control of the inquiry into the poisoning of Yushchenko, with officials close to the government taking charge of two investigations.

The decision by a parliamentary committee to reopen its investigation follows a similar move by the country's prosecutor, an appointee of outgoing President Leonid Kuchma.

Yushchenko, the opposition leader, praised Prosecutor General Svyatoslav Piskun on Sunday for reopening the inquiry after doctors at an Austrian clinic determined over the weekend he had been poisoned by dioxin (search). But he said he hoped the investigation would be conducted after the Dec. 26 election because he didn't want the vote to be influenced by it.

A parliamentary decision is required before the commission actually begins work.

December's repeat vote was ordered by the Supreme Court after it determined last month's second-round election was fraudulent. Yushchenko's rival, Prime Minister Viktor Yanukovych, had been declared the winner of that vote.

Getting to the bottom of what happened to Yushchenko is fraught with troubles because many people — both in business and politics — stood to gain from sidelining him.

"So far we don't have an independent source of information which could allow us to analyze the situation," said Mikhail Pohrebinsky, a Kiev-based political analyst with ties to Kuchma. He said that all of the scenarios about Yushchenko's poisoning "are politically motivated and far from the truth."

Pro-Yushchenko lawmaker Yuriy Pavlenko speculated that Russian agents may have been involved — a popular local theory stemming from Russian President Vladimir Putin's backing of Yanukovych.

Many of the ruling political and business elite faced the loss of lucrative contracts made possible by high level connections if Yanukovych — Kuchma's hand-picked successor — lost the race, analysts said.

Many of those contracts involve Russia. All but one of Russia's major infrastructure links and natural gas exports to Europe pass through Ukraine.

The Ukrainian port of Odessa is a key regional trading outlet to the Black Sea and Middle East, while the naval base in Sevastopol is Russia's only deep-water port on the entire Black Sea coast. Russia also imports food from Ukraine and, in return, the country of 48 million is a key consumer of Russian goods.

Taras Chornovil, Yanukovych's campaign manager, said it was possible that someone connected to Kuchma might have had a role. Or, it could have been someone from Yushchenko's own entourage looking to manipulate a sick president, he said.

Lawmakers from Yushchenko's party have said the Austrian clinic's findings confirmed that his opponents wanted to assassinate him rather than take the risk he would defeat Yanukovych. But some analysts, such as Markian Bilynskyi, suggest that the point of the attack was to sideline Yushchenko just long enough for him to drop from the public eye and lose support.

"The idea wasn't to kill him, to assassinate him," Bilynskyi said. "That would have turned Kuchma into a pariah. That would have been too obvious."

Government opponents have faced attack before. More than two dozen Ukrainian politicians, high-ranking businessmen and journalists have died under suspicious circumstances during Kuchma's decade in power. All investigations into the deaths have proved inconclusive.

For his part, Yanukovych said he sympathized with his rival and that he wished him "no evil."

In an interview with The Associated Press, he demanded a thorough investigation and promised not to interfere in it. But he stressed that the impact of the dioxin could hamper Yushchenko's performance should he be elected in this month's rerun.

"The fact of the matter is that Yushchenko is seriously ill," he said. "We can all see it."

While high concentrations of dioxin, a byproduct of industrial processes, remain in his blood, doctors said Yushchenko's organs have not been damaged and he is fit for the campaign trail. His prognosis depends on which dioxin he ingested — which is as yet unknown — and in what amount.

The new investigations are the second by parliament and the prosecutor.

A parliament commission led by the same lawmaker, Volodymyr Sivkovych, concluded in October that Yushchenko had suffered a combination of a viral infection and several other diseases. Prosecutors also said they could not determine he was poisoned.

"All those scenarios are more public relations than truth," Sivkovych said, casting doubt on whether poisoning could be proven.