Judge Tarek Bitar on Monday received a request demanding his removal from the Beirut port blast case, which effectively suspends his probe pending a decision from the Court of Appeals.
The development follows a lawsuit filed by ex-interior minister Nouhad al-Mashnouq.
The Court of Appeals will now have to decide whether to recuse Bitar or keep him on the case.
Sessions to interrogate retired army officers Camille Daher and Ghassan Gharzeddine were meanwhile called off after Bitar was suspended.
The petition to remove Bitar was filed by Mashnouq’s lawyer on Friday.
Former public works minister Youssef Fenianos had on Wednesday filed a similar request, citing “legitimate suspicion” over Bitar’s handling of the case.
The developments are the latest in a year-long saga surrounding the investigation into the explosion.
Months into the probe, the former lead judge running the investigation, Fadi Sawwan, was removed by the Court of Cassation after similar charges were filed against him by senior government officials.
The judge has accused Mashnouq, Fenianos and two other former ministers of intentional killing and negligence that led to the deaths of more than 200 people in the explosion. Over 6,000 were injured in the massive blast that also devastated a large section of Beirut.
Bitar has also subpoenaed ex-PM Hassan Diab after the latter failed to attend a hearing session.
Bitar’s removal, if it happens, would likely be the final blow to the probe, making it highly unlikely that a third judge would take up the job amid threats by members of the country’s political elite who have closed ranks in their effort to block the probe.
Families of the victims of the explosion have already demanded an international probe, not trusting the Lebanese probe. Lebanon is known for a culture of impunity that has prevailed for decades, including among the entrenched political elites.
The political campaign against Bitar began in July when he announced intentions to go after senior Lebanese officials, and summoned for questioning then-outgoing Prime Minister Hassan Diab, three former Cabinet ministers and top security officials.
None showed up for questioning; the parliament failed to lift immunity of those summoned — a necessary step before any prosecution — while Diab’s office and then-interior minister, Mohammad Fahmi, declined to let Bitar question the heads of two security agencies.