MIAMI (AP) — The Justice Department is preparing to seek an indictment against former Cuban President Raúl Castro, three people familiar with the matter told The Associated Press on Friday, as President Donald Trump threatens possible military action against the communist-run island.

One of the people told the AP that the potential indictment is connected to Castro's alleged role in the 1996 shootdown of four planes operated by the Miami-based exile group Brothers to the Rescue. Castro was defense minister at the time.

All three people spoke on the condition of anonymity because they weren't authorized to discuss an ongoing investigation.

The potential indictment — which would need to be approved by a grand jury — was reported earlier by CBS.

The AP reported in March that the U.S. Attorney in Miami had created a special working group of prosecutors and federal law enforcement to build cases against top Cuban officials amid calls by several south Florida Republicans to reopen its investigation into Castro’s alleged role in the 1996 shootdown. To date, the U.S. has convicted only a single person of conspiracy to commit murder in connection to the shootdown.

As Trump seeks to wind down the war in Iran, speculation has been growing he may soon turn his attention back to Cuba after pledging earlier this year a “friendly takeover” of the country if its leadership didn’t open up its economy to American investment and kick out U.S. adversaries.