(Bloomberg) -- President Donald Trump said the U.S. military thinks a massive explosion at Lebanon’s main port that rocked Beirut may have been caused by an attack.

U.S. military officials “seem to think it was an attack. It was a bomb of some kind,” Trump told reporters at the White House on Tuesday.

“Well, it would seem like it, based on the explosion. I met with some of our great generals and they just seem to feel that it was,” Trump said. “This was not some kind of a manufacturing explosion type of event.”

The White House National Security Council had no comment.

Authorities in the country say it was caused by highly explosive materials at the port, but didn’t say whether it was an accident or an attack. The casualty toll continued to climb through the night on Tuesday, with the health minister saying around 11 p.m. that 67 people were killed and some 3,600 injured.

Prime Minister Hassan Diab described the blast as a “major national disaster” and said the depot that was the reason for the blast had been there since 2014.

“I will not rest until we hold whoever is responsible accountable and punish them with the most severe punishment,” he said. “It’s unacceptable that 2,750 tons of ammonium nitrate have been stored in a container in a depot for the past six years,” he said during a meeting of the Higher Defense Council.

Video footage showed what appeared to be a fire, followed by crackling lights and then a much larger explosion as an enormous cloud of smoke rapidly engulfed the area around the Port of Beirut. Buildings in the area and miles away were severely damaged, including the electricity company and other government entities.

(Updates with description of the scene in eighth paragraph)

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