The death toll from a massive blast that rocked Beirut Tuesday has risen to at least 78 people — with officials blaming a shipment of ammonium nitrate that sat in a warehouse since 2013 for the deadly explosion that also injured nearly 4,000.

The Lebanon defense council declared the port area of the country’s capital a “disaster zone.”

“It is unacceptable that a shipment of ammonium nitrate estimated at 2,750 tons has been present for six years in a warehouse without taking preventive measures that endanger the safety of citizens,” Lebanese Prime Minister Hassan Diab said, according to USA Today.

It was not known what ignited the shipment.

But although the initial assessment by authorities is that the deadly explosion was likely a tragic accident, intelligence sources told Fox News Tuesday that they have not entirely ruled out foul play — ammonium nitrate, used as a fertilizer, was used in the 1995 Oklahoma City bombing.

“Currently, it appears that the explosion in Lebanon was not the result of a military strike,” Jonathan Schanzer, senior vice president at the Foundation for Defense Democracies, told the network. “For now, this explosion appears to be the result of ineptitude.”

“But the ongoing tensions make it clear that future explosions may be the result of something more deliberate,” Schanzer said. “These tensions also come at a particularly bad time for Lebanon.”