At least one person was killed and up to 25 were injured by the explosion in Abadan, in Iran's oil-rich southwest, according to accounts by domestic Iranian news agencies. One Abadan resident quoted by the Associated Press said he saw rescue vehicles rushing to the site.
Officials quickly insisted that blast was the result of an industrial accident and not an act of sabotage. Iran's industrial sector has long been riddled by deadly accidents, with train and plane crashes, troubles at petrochemical facilities and other incidents.
According to the semi-official Mehr news agency, the explosion and fire were caused by a gas leak, which poisoned oil workers.
An uprising by the country's ethnic Arab minority, which was inspired by pro-democracy movements across the Middle East and brutally crushed by authorities, has also been smoldering in the country's southwest.
At least one official all but accused Ahmadinejad, who had recently appointed himself caretaker oil minister amid howls of protest by his many political rivals, of rushing to open the plant too early in order to ingratiate himself with Iranians. The refinery will eventually produce 1.5 million gallons of gasoline a day to satiate Iran's energy-hungry consumers.
Hamid-Reza Katouzian, head of parliament's energy committee, told the semi-official Fars news agency that experts had warned officials that Abadan was not ready to launch.
"There was a technical fault at the refinery," he was quoted as saying. "The incident was not deliberate sabotage."