A report by the company was reviewed by Lebanon's nuclear energy authority and the materials were found to be dangerous nuclear substances, a statement by the country's higher defense council quoted Diab as saying.
Diab's cabinet has served in a caretaker capacity since quitting last August over the huge Beirut port blast that killed 200 people and compounded the country's financial collapse.
In his statement on Wednesday, Diab said the political deadlock spurred calls to activate his cabinet but that the question of whether the constitution allows it was up to the parliament.
Lebanon's Diab has tasked the defence minister, environment minister and the National Council for Scientific Research with the follow-up, a statement from his office said.
The United Nations interim forces in Lebanon will be informed to draw up an official report, the statement said.
Lead investigative judge Fadi Sawan this month charged Diab and three former ministers over the explosion in the first set of indictments against politicians.
The decision was made during a cabinet meeting that followed four ministerial resignations over the August 4 blast that left at least 160 dead and devastated swathes of Beirut.