BEIRUT, July 9 (Reuters) - A Lebanese minister has denied a request by the judge probing the Beirut port explosion to question a top security official, a document seen by Reuters on Friday showed, as attempts to deliver justice over the catastrophe continue to flounder. Nearly a year after the Aug. 4 explosion, which killed more than 200 people, wounded thousands and devastated swathes of the capital, many Lebanese are furious that no senior officials have been held to account. The blast was caused by a massive quantity of explosive chemicals that had been stored unsafely at the port for years. The request from Judge Tarek Bitar to question Major General Abbas Ibrahim, head of the powerful General Security agency, was rejected by caretaker interior minister Mohamed Fahmy in a letter to the justice minister. In a statement, Ibrahim said he was subject to the law like all Lebanese, but the probe should take place "far away from narrow political considerations". Bitar became the lead investigator into the blast after his predecessor, Judge Fadi Sawan, was removed in February following requests from two former ministers he had charged with negligence over the blast. Sawan had charged three ex-ministers and the outgoing prime minister Hassan Diab with negligence. But they refused to be questioned as suspects, accusing him of overstepping his powers. A parliamentary committee convened on Friday to study a request by Bitar for immunity to be lifted from former Finance Minister Ali Hassan Khalil, former Public Works Minister Ghazi Zeaiter and former Interior Minister Nohad Machnouk. After being charged, Diab said his conscience was clear, Khalil said he had no role in the blast, and Zeaiter called the charges "a blatant violation". Machnouk has also denied any responsibility. The committee postponed its decision to an unspecified date as parliamentarians said more correspondence was needed with Bitar to take a decision on the matter. Families of the victims protested nearby, some holding photos of their relatives, to expressing their anger against the interior minister and parliament speaker Nabih Berri. "Those who don"t submit to questioning by the judge, immunity or no immunity, they will be our target," said Youssef al-Mawla, who lost his son in the blast.