BEIRUT — 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. The Port of Beirut and customs office is notorious for being one of the most corrupt and lucrative institutions in Lebanon where various factions and politicians, including Hezbollah, hold sway.

The investigation is focusing on how 2,750 tons of ammonium nitrate, a highly explosive chemical used in fertilizers, came to be stored at the facility for six years, and why nothing was done about it.

Losses from the blast are estimated to be between $10 billion to $15 billion, Beirut Gov. Marwan Abboud told Saudi-owned TV station Al-Hadath, adding that nearly 300,000 people are homeless.

“Beirut as we know it is gone and people won’t be able to rebuild their lives,” said Amy, a woman who swept glass from a small alley beside by a tall building that served as a showroom for a famous Lebanese designer and was a neighborhood landmark.