The judge heading Lebanon’s investigation into the devastating Beirut port explosion suspended the interrogation of former Prime Minister Hassan Diab on Thursday after Diab filed a suit questioning the judge’s authority, a legal source said.

The suit, filed on Wednesday, is the latest in a series of cases that have derailed Judge Tarek Bitar’s attempts to question top officials over last year’s blast that killed more than 215 people, injured thousands and destroyed large swathes of the city.

Diab, who has been charged in connection with the explosion, had already missed at least two interrogation sessions.

The investigation has made little headway amid a smear campaign against Bitar and pushback from powerful Lebanese factions, angering many Lebanese that one year on no senior official has been held accountable as the country faces economic and financial meltdown.

The row over the probe has paralysed the cabinet with Prime Minister Najib Mikati suspending sessions until a solution to the standoff is found.

The dispute spilt over on Oct. 12 when ministers allied to the powerful Iran-backed Hezbollah group and its ally, the Amal movement, called for Bitar’s removal in a heated discussion during the last cabinet session.

Bitar was officially notified of Diab’s legal suit arguing that he did not have the authority to interrogate the former prime minister which automatically forced him to suspend the session, the legal source said.

“The suspension of questioning relates only to Diab in this case,” the source told Reuters.

Bitar has sought to question top politicians, including former ministers and members of parliament, since July but nearly all have spurned him with some raising legal complaints questioning his impartiality.

Potential foreign aid donors have called for a transparent investigation into the Aug. 4, 2020, blast, caused by a huge quantity of unsafely stored ammonium nitrate.

Bitar has in the past issued arrest warrants for ministers who failed to show up for interrogation, and Diab’s lawsuit was likely an attempt to prevent the same happening to him after his interrogation scheduled for Thursday.

Former interior minister and Sunni Muslim MP Nohad Machnouk, whose interrogation is scheduled for Friday, will file a similar suit on Thursday, his lawyer confirmed to Reuters.

Should Bitar be notified of the suit ahead of Friday’s scheduled session, that would be suspended as well.