Robert Levinson, 68, of Coral Springs, Florida, a private investigator and former agent for the Federal Bureau of Investigation who was also a part-time consultant for the Central Intelligence Agency, has been missing since disappearing from Iran’s Kish Island during what has since been revealed as a rogue CIA operation.

The New York Times reported Sunday, citing a spokeswoman for the National Security Council, that administration officials had contacted Levinson’s relatives to assure them that his case was a priority. “The U.S. government will never cease its efforts to bring back our citizens who are unlawfully detained or missing overseas,” an NSC statement said, according to the newspaper.

As a candidate in 2015, President Donald Trump vowed to bring Levinson home.

Under President Barack Obama, five Americans were released by Iran in January 2016 in an exchange timed to coincide with the implementation of the sanctions relief for nuclear rollbacks deal struck between Iran and six major powers. Levinson was not one of those released, but the Obama administration, which had brokered the deal, accepted an Iranian pledge to help track his whereabouts. The information provided led to dead ends, the New York Times reported Sunday.

Some American officials believe that Levinson died in captivity, or that he is no longer being held in Iran. Throughout its time in office, the Obama administration continued to say that bringing Levinson home was a top priority.

Levinson family members told the newspaper that they believe he is still alive, and hope that the Trump administration will be more aggressive with Iran about getting information on his whereabouts.