Federal prosecutors in Miami were ordered to open a new criminal investigation targeting detained former Venezuelan leader Nicolás Maduro amid some concerns that the pending prosecution against him is weak, multiple sources familiar with the matter told CBS News.

The new probe comes as Alex Saab, a close business associate of Maduro who served as Venezuela's minister of industry and national production, was deported to the U.S. and indicted for his alleged role in a money-laundering conspiracy scheme involving a Venezuelan public welfare food program.

Maduro and his wife Cilia Flores were captured by U.S. forces on Venezuelan soil in early January and transported to New York City to face narco-trafficking and firearms charges.  

He was initially charged in a superseding indictment dating to 2020, while Bill Barr was attorney general.

Both have pleaded not guilty.

The order from senior Justice Department leaders to open a new criminal case in Miami against Venezuela's former leader was issued after Maduro was already in custody on the New York-based charges, the sources said. 

A Justice Department spokesperson declined to comment.

An attorney for Maduro declined to comment on the new criminal investigation. 

The new investigation was formally opened around March, the sources said, and Michael Berger, a respected Miami-based prosecutor who specializes in international criminal cases, was assigned to oversee the effort, along with several agents from the FBI and Homeland Security Investigations. IRS Criminal Investigation is also involved, sources added.

That same month, a group of prosecutors and agents convened a meeting to discuss any open investigations that involved Maduro or Alex Saab. 

Saab served two years in a U.S. prison on money-laundering charges after he was extradited to the United States from Cape Verde. But President Joe Biden later pardoned him in 2023, and he was returned to Venezuela as part of a prisoner swap with Maduro's government.

Saab was an unindicted co-conspirator in a 2021 case filed in the Southern District of Florida that charged five defendants in a foreign bribery and money-laundering scheme tied to a Venezuelan state-owned and controlled food program, according to two sources familiar with the matter. 

The indictment made public on Monday charges him with money laundering involving the same Venezuelan-controlled food program known as CLAP, the Comité Local de Abastecimiento y Producción, that was at the heart of the 2021 case. The alleged crimes now extend through January, and he is charged with a single count.

The other defendants' names are redacted. The new Saab indictment was secured in January, not long after Maduro was brought to the U.S. to face charges.

An attorney for Saab did not respond to a request for comment.

Federal prosecutors have shown significant interest in Saab's activities because they believe he controls some of Maduro's money. 

Agents and prosecutors in South Florida have long tried to link Venezuelan leaders to financial crimes in the U.S., but those efforts have proven elusive because of the challenges tracing accounts and money flows directly to them, some of the sources said.

One of the highest-level former Venezuelan government officials to face justice in the Southern District of Florida in recent years was Alejandro Andrade Cedeno, the former national treasurer, who was sentenced in 2018 for his role in a billion-dollar currency exchange and money laundering scheme.

One concern that Justice Department and White House officials have privately expressed about the pending indictment in New York against Maduro is the lack of any money-laundering charges, one source said.

The indictment alleges that Maduro provided "diplomatic passports to drug traffickers and facilitated diplomatic cover for planes used by money launderers to repatriate drug proceeds from Mexico to Venezuela." 

He faces charges on narcoterrorism and cocaine importation, possession of machine guns and conspiracy to possess machine guns.

However, analysts and experts who previously spoke with CBS News after Maduro was indicted said that much of the cocaine that comes into the United States actually bypasses Venezuela. According to the Drug Enforcement Administration, most of the cocaine coming into the U.S. comes from Colombia. 

Some analysts have doubts about the strength of the case in New York, which portrays Maduro as a central figure in facilitating the drug trade.