Iran gained access to secret UN nuclear watchdog documents two decades ago, which helped Tehran mislead investigators, The Wall Street Journal said Wednesday.

The IAEA began investigating Iran for secret nuclear work in 2002, after information was shared by an Iranian opposition group of a possible hidden weapons program.

WSJ has reported that according to some of the documents it has reviewed, it appears that Tehran shared the secret IAEA material with top political, military and nuclear officials to devise misleading answers to the UN watchdog.

The proof of illegally obtained documents was among a throve of archives Israel stole from Iran and disclosed in 2018. Some IAEA documents bear comments and notes in Persian, showing officials used the confidential information to devise answers that would satisfy nuclear inspectors.

While Iran was able to surmise what the IAEA already knew, it volunteered the information to the agency while being able to hide what it really wanted to keep secret.

It is not clear how Iran obtained the IAEA documents, but a major security breach is suspected.

The revelation can have an impact on ongoing issues between Iran and the IAEA, which is still asking questions about unexplained traces of radioactive material in some sites investigated by inspectors since documents revealed by Israel showed secret work on a weapons’ program.

This in turn can impact stalled negotiations between Iran, the United States and other world powers to revive the 2015 nuclear agreement known as the JCPOA.