Iran’s underground Fordo nuclear plant was indeed hit by an explosion sometime last week, and Iranian officials suspect the Mossad or CIA as responsible actors, the former Iranian intelligence officer who initially broke the story said Monday.

In an interview with Channel 2 News, Hamidreza Zakeri surmised, however, that an Iranian “internal action” could also have been at play.

Some 240 people were working at the plant at a depth of 90 meters at the time of the incident, according to Zakeri. He said that the two elevators normally available for transfer to the surface are now out of order and it is unknown if workers were hurt or killed in the explosion.

Channel 2′s Middle East analyst Ehud Yaari said that the IAEA would know within days if a blast had actually occurred at the plant. According to Yaari, the UN nuclear watchdog has cameras placed at Fordo, which it inspects every seven to 10 days.

The explosion reportedly occurred last Monday, so if Iran doesn’t let the IAEA inspectors into the facility in the next two or three days “we’ll know something happened,” he said. 

The White House on Monday dismissed reports that there was a blast at the facility.

“We have no information to confirm the allegations in the report and we do not believe the report is credible,” press secretary Jay Carney said. “We don’t believe those are credible reports.”

Israeli intelligence officials confirmed that a major explosion had rocked an Iranian nuclear facility, The Times of London reportedThe British daily on Monday cited officials in Tel Aviv to the effect that the blast had occurred last week, as originally reported on the website wnd.com.

Iran is not believed to have evacuated the area surrounding the Fordo plant, according to the same Israeli sources, who said that an investigation into the blast was ongoing.

“We are still in the preliminary stages of understanding what happened and how significant it is,” one Israeli was quoted by the London Times as saying. He did not know if the explosion was “sabotage or accident” and refused to comment on rumors that Israeli aircraft were seen near Fordo at the time of the blast.

On Sunday, Israel’s Home Front Defense Minister Avi Dichter welcomed the report of the blast, saying, “Any explosion in Iran that doesn’t hurt people but hurts its assets is welcome.”

Yoel Goldman contributed to this report.