BEIRUT – Hezbollah has threatened to "usurp" the Lebanese judge investigating the Beirut port blast in a verbal message to him in recent days, a source familiar with the conversation has told CNN. ​

High-ranking Hezbollah official Wafiq Safa ​issued the threat to Judge Tarek Bitar through an ​unnamed intermediary, who relayed the contents of the message, according to the source. ​The intermediary was someone the judge knew and trusted, the source said, and mentioned Safa by name. ​

Safa is head of the Iran-backed militant group's Liaison and Coordination Unit. In 2019, he was placed on a US Treasury sanctions list, accused of having "exploited Lebanon's ports and border crossings to smuggle contraband and facilitate travel" on behalf of Hezbollah. ​

"We've had it up to our noses with you. We will stay with you until the end of this legal path, but if it doesn't work out, we will usurp you," the message to Bitar said, according to the source.

Neither Safa nor other members of Hezbollah have been named by state media as official subjects of the investigation into the port blast.

Judge Tarek Bitar's investigation into the port blast has rattled the political establishment in Lebanon.

The conversation was first reported by Lebanese Broadcasting Corporation correspondent Edmond Sassine in a tweet on Tuesday.

It is unclear what was meant by ​the threat to "usurp" Bitar, but the warning has raised concerns that the judge could be at risk of being physically harmed.

Hezbollah, which has a political arm consisting of elected members of parliament, has previously been accused of employing intimidation tactics against officials.

The group has not responded to CNN's request for comment, and it has not issued a public response.

​Since his appointment in February of this year, the judge, who also heads Beirut's criminal court, has sought top political and security officials for questioning in the Beirut blast probe. He is the second judicial investigator to head the investigation. The first judge tasked with handling the probe was dismissed after two ex-ministers charged in the investigation successfully filed a motion for his removal.

Bitar's ​investigation of high-profile politicians -- including former ministers, the head of the country's main intelligence apparatus and former Prime Minister Hassan Diab -- has posed the biggest legal challenge to Lebanon's ruling elite in decades. ​Diab has repeatedly denied the accusations against him.

​Many in the ruling elite, including politicians, have immunity in the investigation by virtue of Lebanon's constitution, but there have been growing calls for that immunity to be lifted for the purposes of this investigation. There are ongoing legal battles, in return, to maintain that immunity and avoid prosecution.

Meanwhile, Bitar has emerged as one of the country's most popular civil servants, hailed for championing rule of law in a confessional power sharing system that has repeatedly shielded powerful politicians and businessmen from accountability.

Dozens of members of parliament​, including all from Hezbollah's parliamentary bloc, have petitioned to take the case out of Bitar's hands and move it to a previously unknown "judicial council" which activists and legal experts say would be heavily influenced by the accused. The move ignited a social media campaign against the so-called "deputies of shame."

A huge blast at Beirut's port on August 4, 2020, killed more than 200 people and injured thousands more. The explosion, which laid waste to whole neighborhoods, was caused by the ignition of hundreds of ​metric tons of explosive ammonium nitrate that were improperly stored in a warehouse for over six years.

At least six urgent letters sent by customs officials since 2014 ​-- the year the material was unloaded at the port under mysterious circumstances -- had alerted the authorities to the danger posed by the chemicals.

Successive leaders -- four governments and three prime ministers -- either would have or should have known about the threat posed by the material, yet little was done to address the danger. ​

Bitar's probe has been investigating several politicians for "criminal neglect."

Though the judge has not sought to question Hezbollah officials, ​according to the lists made public in state media, the group has emerged as one of the most vocal opponents of the investigation.

In a recent televised speech, Hezbollah chief Hassan Nasrallah lambasted the probe, accusing Bitar​ of being "politicized." Nasrallah offered no evidence to support the claim which was seen as a vociferous defense of the group's political allies who have been targeted in the investigation.

Over the last two decades, Hezbollah has evolved into one of the most sophisticated armed groups in the Middle East​. Nasrallah has said the group's arsenal includes precision-guided missiles.

In 2000, the group drove Israeli forces out of south Lebanon, ending a 22-year occupation. In 2006, they withstood a 33-day Israeli assault on Lebanon aimed at dislodging them. In 2013, the group joined Syria's civil war on behalf of President Bashar al-Assad in a move that is widely credited with having prevented the immediate toppling of the Syrian dictator, extending the regime's life until Russia's intervention in 2015 definitively tipped the balance in Assad's favor.

Hezbollah has also been a vocal critic of a popular uprising that began nearly two years ago against the country's ruling elite and accused the US and Western consulates of supporting the protests.