An explosion rocked western Tehran early Friday, state media reported, causing widespread power failures in two residential areas and unnerving Iranians awakened for the third consecutive week by an early-morning blast. The precise location of Friday’s explosion was unclear, but analysts said there were several military and training facilities in the area that could be the target of sabotage. A cause was not immediately determined.

“There are two underground facilities, a site associated with chemical weapons research and an unidentified military production site,” said Fabian Hinz, an Iran military expert and research associate at the James Martin Center for Nonproliferation Studies. Iranian officials gave contradictory statements about the event.

The mayor of Garmdareh, a nearby town, said the sound heard by residents was an “explosion at a factory making gas cylinders.” But even though state media had already reported the blast, the member of Parliament from the affected area, Hossein Haghverdi, said there was no explosion and that the power outage had been caused by some temporary problem at a local power station.

Iran described the Khojir episode as a gas tank explosion. Independent analysts said it was unclear whether the cause was an accident, sabotage or something else, although they noted that Iran had initially given a misleading location. Iran has not publicly disclosed the results of its investigation into the Natanz explosion, citing national security concerns.

But a Middle Eastern intelligence official with knowledge of the episode said Israel was responsible for the attack on the Natanz nuclear complex, using a powerful bomb. A member of the Islamic Revolutionary Guards Corps who was briefed on the matter also said that an explosive was used.