The investigation into Beirut’s <a href="https://www.thenationalnews.com/tags/beirut-explosion/" target="_blank">deadly port blast</a> is still going ahead despite numerous legal hurdles and <a href="https://www.thenationalnews.com/mena/lebanon/2021/10/14/lebanon-protests-why-has-shooting-broken-out-over-the-beirut-port-explosion/" target="_blank">street clashes that left seven people dead last week</a>. The <a href="https://www.thenationalnews.com/tags/lebanon/" target="_blank">Lebanese</a> Parliament reconvened on Tuesday for the first time since giving its vote of confidence to new Prime Minister Najib Mikati on September 20. This enhances the legal protection of sitting MPs, but lawyers say that investigative judge Tarek Bitar can continue procedures launched against several officials in the past month. Mr Bitar has evidence implicating some of the most prominent former ministers and sitting MPs in the explosion that <a href="https://www.thenationalnews.com/mena/lebanon/2021/09/28/beirut-port-blast-claims-another-victim-13-months-later/" target="_blank">killed more than 215 people</a> on August 4, 2020, allegedly caused by the improper storage of thousands of tonnes of ammonium nitrate for seven years. Here's what we know. Mr Diab was sworn in in January 2020 and resigned on August 10, following the Beirut blast, but remained caretaker prime minister for more than a year until Lebanon’s political class agreed on his successor, Najib Mikati, on September 10. Mr Bitar’s predecessor, Fadi Sawan, charged Mr Diab on December 10, 2020, as well as two former public works ministers, Ghazi Zeaiter and Youssef Fenianos, and former finance minister Ali Hassan Khalil. Mr Sawan was removed in February following a complaint by Mr Zeaiter and Mr Khalil, who belong to the same political party, the Amal Movement. They are both sitting MPs. Mr Bitar summoned Mr Diab for questioning on August 26, which the former prime minister ignored. Mr Bitar issued a subpoena for him to appear on September 20. Mr Diab failed again to appear for questioning because he left the country for what he said was a personal visit to the US on September 14. Mr Bitar issued a second subpoena, following Mr Diab’s change of address, and postponed the interrogation first to October 4 and then to October 28. A subpoena is not the same as an arrest warrant. “A subpoena requires the person to comply with a court request and may lead to civil and or criminal penalties being applied if the person does not," said Aya Majzoub, Lebanon and Bahrain Human Rights Watch researcher. "An arrest warrant may be an outcome of failing to abide by the subpoena and show up to questioning." Mr Diab returned to Lebanon on October 12, according to a former advisor. The former prime minister currently has no known employer. Mr Bitar issued an arrest warrant against Mr Khalil on October 12 after he failed to appear for interrogation. Mr Khalil is charged with homicide with probable intent, negligence, injury and arson. Mr Khalil, Mr Zeaiter and former interior minister Nohad Machnouk filed a complaint against Mr Bitar at Beirut’s court of appeals, which it rejected on October 4. Mr Khalil and Mr Zeaiter also filed two lawsuits at the court of cassation, which were turned down on October 11 and October 14. All complaints were rejected for lack of jurisdiction, said Ghida Frangieh, a lawyer with NGO Legal Agenda. The court of appeal fined the three men the maximum possible amount of 800,000 Lebanese pounds. "It proves they're abusing their right to litigate," said Ms Frangieh. Mr Khalil cannot be arrested while Parliament is in session. It started Tuesday and will last until the end of the year. But there is a loophole – article 97 of the House of Representatives' bylaw states MPs can continue being interrogated during a parliamentary session without asking for Parliament’s authorisation unless parliamentarians hold a meeting and decide against it, said Wissam Lahham, a constitutional expert at Beirut’s Universite Saint Joseph. It remains highly unlikely that Parliament would allow Mr Bitar to question additional sitting MPs while it is in session, said Mr Youssef Lahoud, a lawyer who represents more than 1,200 victims of the blast. Mr Bitar issued an arrest warrant against Mr Fenianos on September 16, after he failed to appear for questioning. So far, only Mr Fenianos and Mr Khalil are subject to arrest warrants. Unlike Mr Khalil, Mr Fenianos is not a sitting MP and is thus not protected by parliamentary immunity. Mr Fenianos, a lawyer, is also charged with homicide with probable intent, negligence, injury and arson. He has not yet been arrested. An army representative said it was up to the police to arrest Mr Fenianos. The police were not immediately available for comment. “The prosecution and the police are responsible to execute the arrest warrant. The Minister of Interior declared he instructed the police not to execute the warrant,” said Ms Frangieh. Scheduled interrogations of Mr Machnouk, a sitting MP, on September 30 and October 13 were postponed because the probe was suspended at the time. Mr Machnouk currently enjoys the same parliamentary protection as Mr Khalil. Local television Al Jadeed reported on Tuesday that Mr Machnouk and Mr Zeiater are expected to appear for interrogation on October 29. Two lawsuits, which requested the judge's transfer for legitimate suspicion, remain pending at the court cassation. They were filed by Mr Machnouk and Mr Fenianos. They are similar to the lawsuit that removed Mr Sawan from the case, said Ms Frangieh.