Iran has executed a nuclear scientist who mysteriously turned up in the United States six years ago and returned to Tehran a few months later, authorities said Sunday, in the first official confirmation of the researcher’s fate since he arrived back in his homeland.

Iranian officials offered no details about the charges against Shahram Amiri, whose case has left unanswered questions about whether he voluntarily defected to the United States or — as he claimed — was abducted by agents while on a religious pilgrimage in Saudi Arabia in 2009.

Amiri surfaced in 2010 in videos posted online from an undisclosed location in the United States. Later that year, he arrived unannounced at the Iranian interests section at the Pakistani Embassy in Washington and demanded to be sent home.

An Iranian judiciary spokesman, Gholamhossein Mohseni Ejei, told reporters in Tehran that Amiri was convicted of spying charges as he “provided the enemy with vital information of the country,” according to state-run media. But Ejei did not shed light on why Amiri’s detention and trial where carried out in secret, or the extent of the alleged information passed.

It also was unclear when the execution occurred, but Iran carried out several hangings on Tuesday, and a death notice later appeared in Amiri’s home town of Kermanshah, about 300 miles southwest of Tehran, the Associated Press reported, citing the Iranian reformist newspaper Shargh.

Amiri’s disappearance in 2009 came amid targeted killings in Iran of scientists and others associated with the country’s nuclear program – attacks that Iran blamed on the United States and Israel. A deal last year between Iran and world powers to limit Tehran’s nuclear program cleared the way for the easing of some international sanctions, but it has been met by opposition from powerful hard-line groups in Iran, including the judiciary and Revolutionary Guard Corps.

Although the circumstances of Amiri’s months in the United States remain murky, the case unfolded during Hillary Clinton’s time as secretary of state — raising the prospect that it could become another element in the presidential campaign. Republican nominee Donald Trump has denounced the nuclear deal and other Obama administration decisions regarding Iran.

Amiri claimed he was forcibly held by Saudi and American agents and then transferred to the United States. “I was under the harshest mental and physical torture,” he said after returning to Iran in a propaganda-heavy ceremony broadcast across Iran.

Amiri was embraced by his family and greeted by a senior envoy from Iran’s Foreign Ministry. Amiri smiled and gave the V-for-victory sign.

U.S. officials said at the time, however, that Amiri, an expert in radiation detection, agreed to leave Iran and was offered $5 million to provide information on his country’s nuclear development but left the United States before any payments were made.

Manoto, a private satellite television channel based in London and thought to be linked to Iranian activists, first reported Amiri’s execution on Saturday, citing family members.

Amiri appeared to be mentioned in emails released last year by Clinton as part of probes into her use of a private server while serving as secretary of state. An email forwarded to Clinton on July 5, 2010 — nine days before Amiri returned to Tehran — apparently refers to Amiri’s case.

“We have a diplomatic, ‘psychological’ issue, not a legal one. Our friend has to be given a way out,” wrote Richard Morningstar, who was then a State Department special envoy for Eurasian energy affairs. “We should recognize his concerns and frame it in terms of a misunderstanding with no malevolent intent and that we will make sure there is no recurrence.”