A number of Beirut port officials are being placed under house arrest pending an investigation into Tuesday's huge explosion.
The blast killed at least 135 people and injured more than 4,000 others. A two-week state of emergency has begun.
Officials said the blast was caused by 2,750 tonnes of ammonium nitrate stored unsafely in a warehouse.
Customs chief Badri Daher said his agency called for the chemical to be removed, but "this did not happen".
He says they leave it to the experts to determine the reasons.
Ammonium nitrate is used as a fertiliser in agriculture and as an explosive.
[Source: BBC]
