A blast in a mosque in Iran that killed at least 10 people was an accident and not an attack, a senior Interior Ministry official said on Sunday.
Iranian media had reported that a bomb exploded in a crowded mosque in the southern city of Shiraz on Saturday evening, also wounding more than 160 people.
"Last night's explosion in Shiraz was as a consequence of an accident and not the planting of a bomb," the official IRNA news agency quoted the deputy interior minister in charge of national security, Abbas Mohtaj, as saying.
He did not give details, but state Press TV television said the blast may have been "caused by explosives left behind from an earlier exhibition commemorating" the 1980-88 Iran-Iraq war.
The semi-official Fars News Agency carried a similar report.
"Based on the initial evaluation, the Saturday night explosion ... has not been intentional or sabotage," it quoted the commander of the security forces in the southern Fars province, Ali Moayedi, as saying.
"The cause of the incident was probably laxness since a defence fair was held at this place some time ago. There is a possibility that the remaining ammunition at this place was the factor behind this explosion," Moayedi said.
Iran's Foreign Ministry spokesman said the investigation was continuing.
"The latest news we have ... is that there was no firm stance by police and security officials as the investigation is still ongoing," Mohammad Ali Hosseini told reporters. "Therefore no pre-judgement can be made about the incident."
Late on Saturday, Fars quoted a police official as saying a "hand-made" device had been planted in the mosque.
State television urged people in Shiraz, a city of more than one million people and also a popular tourist destination, to donate blood for the wounded and said all nurses in the city had been called to report for work.
Iranian media said on Saturday the death toll might rise as some of the wounded were in a critical condition.
IRNA news agency said the blast took place during an address by a cleric in the city's Shohada mosque.
A 20-year-old woman who was wounded by the blast said there were about 800 people inside the mosque at the time. "After we heard an explosion, there was smoke everywhere," Saeedeh Ghorbani said.
Security is normally tight in Shi'ite Muslim Iran and bomb attacks have been rare in recent years. But several people were killed in 2005 and 2006 in blasts in a southwestern province with a large Sunni Arab population.
Tehran has in the past accused Britain and the United States of trying to destabilise the Islamic Republic by supporting ethnic minority rebels operating in sensitive border areas.
