A spying device disguised as a rock at Iran’s Fordo nuclear facility blew up when it was discovered by Iranian security forces, Western intelligence officials told The Sunday Times.

The device, which was discovered last month but only reported on Sunday morning, was capable of collecting data from computers at the nuclear site, which is one of the country’s main enrichment facilities.

The device was happened upon by soldiers on patrol and its remains were examined by Iranian experts after it exploded, according to the Sunday Times.

A significant amount of information tracking Iran’s uranium enrichment activities could have been lost in the explosion, the British paper reported.

Last week, Iran’s vice president revealed that power lines near the plant had been blown up a day before officials from the International Atomic Energy agency requested to inspect the site. He accused the IAEA of harboring saboteurs bent on destroying Iran’s nuclear program

Fordo, buried beneath hundreds of feet of rock, is considered Iran’s most heavily guarded nuclear facility. Officials fear the uranium being enriched at the site’s 3,000 centrifuges will be used to build a nuclear weapons program, a claim Iran denies.

Israel and the US have been accused of mounting a covert war on Iran’s nuclear program, siccing sophisticated computer viruses on nuclear sites to sabotage centrifuges and collect data, and assassinating nuclear scientists.