BERUIT, Lebanon (AP) - Investigators probing the deadly blast that ripped across Beirut focused Wednesday on possible negligence in the storage of tons of a highly explosive fertilizer in a waterfront warehouse, while the government ordered the house arrest of several port officials.International aid flights began to arrive as Lebanon’s leaders struggled to deal with the widespread damage and shocking aftermath of Tuesday’s blast, which the Health Ministry said killed 135 people and injured about 5,000 others.Public anger mounted against the ruling elite that is being blamed for the chronic mismanagement and carelessness that led to the disaster.