Iran says it has no knowledge of the whereabouts of retired FBI agent Robert Levinson, who U.S. authorities have long presumed had been captured there.

In a statement to The Associated Press on Saturday, Iranian press counselor at the United Nations, Alireza Miryusefi, called on the U.S. government to explain Levinson's mission in Iranian territory, after an AP investigation revealed that he had been on an unauthorized assignment for the CIA when he vanished on Iran's Kish Island in March 2007.

Asked about the AP investigation published Thursday, Miryusefi said in an email to the AP that, "Actually the American authority should explain about Levinson's mission in Iranian soil. They are responsible and should respond."

He insisted that the government in Iran has been cooperating with attempts to learn Levinson's fate. The Iranian government has been trying "to find any clue about Levinson's situation for humanitarian and security reasons, but no success," he said.

"We also provided all possible assistance to his family. Unfortunately this case is another America's type scandal," Miryusefi said.

U.S. officials have raised the Levinson case with Iran repeatedly over the years, but until the AP investigation this week it was not known that Levinson was hoping to gather information in his role as an independent contract investigator who expected to be compensated by a group of analysts at the CIA.

The Iranians have also stirred confusion around the Levinson case.

During one meeting between the U.S. and Iran, the Iranians said they were searching for Levinson and were conducting raids in Baluchistan, a mountainous region that includes parts of Pakistan, Iran and Afghanistan, U.S. officials said. But the U.S. ultimately concluded that there were no raids, and officials determined that the episode was a ruse by the Iranians to learn how U.S. intelligence agencies work.

After he vanished, the CIA at first told lawmakers he had previously done contract work for the agency, but he had no current relationship with the agency and there was no connection to Iran. However, in October 2007, Levinson's lawyer discovered emails in which Levinson tells a friend at the CIA he was working to develop a source with access to the Iranian regime. The emails were turned over to the Senate Intelligence Committee, which touched off an internal CIA investigation.

Three veteran analysts were forced out of the CIA and seven others were disciplined as a result of a breach of agency rules.

The last photos and video of a bearded, emaciated Levinson were released anonymously to his family in 2010 and early 2011, and investigators say his trail has grown cold since.

Levinson, who would be 65, has been missing longer than any other U.S. hostage.