A massive explosion and fire at a highly sensitive Iranian nuclear facility last week was likely an act of sabotage, intelligence officials and weapons experts said Monday, but analysts were divided over the severity of the damage to Iran’s nuclear program.

A spokesman for Iran’s nuclear energy agency on Monday said the country’s security agencies knew the cause of the explosion but would provide no details for now, citing “security considerations.” Other Iranian officials have publicly suggested that the United States or Israeli operatives were to blame, although neither country has acknowledged any involvement in the incident.

Other analysts and nuclear experts also said the evidence so far strongly suggests that a bomb detonated inside the facility, known as the Iran Centrifuge Assembly Center.

Iran began sharply increasing its production of low-enriched uranium last year in a protest over the Trump administration’s 2018 decision to unilaterally withdraw from the Iran nuclear deal.

The Middle Eastern security official said the explosion was a “wake-up call” intended to deter Iran after months of ominous advances in that country’s nuclear program.

The operatives who carried out the apparent attack clearly had remarkable penetration of Iran’s nuclear program and detailed knowledge of the facility, he said.

Undoubtedly, it will take Iran many months to rebuild the facility, which means long delays in installing the advanced, high-capacity centrifuges that Iran has been constructing in recent years, said David Albright, a nuclear weapons expert and president of the Institute for Science and International Security, a Washington nonprofit organization that researches nuclear weapons programs.

“As the Iran deal continues to crumble under external pressure, it’s going to make it a lot easier for those who want out of the nuclear deal to push to build more secret facilities — and eventually a bomb,” Lewis said.

Those included recent purported tit-for-tat hacks by Iran and Israel on each other’s public infrastructure and the Stuxnet virus that severely damaged Iran’s nuclear program a decade ago.

A critic of the Iran nuclear deal, Amidror said the agreement left Tehran free to strengthen its expertise in two particularly threatening areas: refining centrifuges and improving long-range missile technologies