Ukraine's outgoing government is attempting to control the inquiry into the poisoning of presidential candidate Mr Viktor Yushchenko.
Officials close to the government are taking charge of both investigations into who tried to harm or kill the leader of the "Orange Revolution."
The head of a new inquiry by lawmakers - an ally of Mr Yushchenko's opponent in the court-ordered December 26th presidential rematch - immediately cast doubt on whether deliberate poisoning could be proven.
The decision by a parliamentary commission to reopen its investigation came a day after a similar move by the country's new top prosecutor.
Mr Yushchenko praised Prosecutor General Mr Svyatoslav Piskun on Sunday for resuming the investigation after an elite clinic in Austria determined over the weekend he had been poisoned by dioxin.
But he said he hoped the investigation would be conducted after the election because he didn't want it to influence the vote "positively or negatively."
The poisoning was not the first time that government opponents have been attacked in this former Soviet republic. More than two dozen Ukrainian politicians, high-ranking businessmen and journalists have died under suspicious circumstances over the past 10 years. All investigations into the deaths have proved inconclusive.