President Trump on Tuesday said that U.S. military generals have informed him that the massive explosion that rocked the Lebanese capital of Beirut earlier in the day – leaving more than 70 people dead – was likely caused by a bomb.

“I've met with some of our great generals and they just seem to feel that this was not some kind of manufacturing explosion type of an event,” Trump said. “They seem to think it was an attack. It was a bomb of some kind.”

The blast flattened much of the city's port, while damaging buildings across the capital and sending a giant mushroom cloud into the sky. Along with the more than 70 deaths, at least 3,000 others were injured.

PHOTOS: HUGE EXPLOSIONS ROCK BEIRUT WITH WIDESPREAD DAMAGE, INJURIES

The blast struck with the force of a 3.5 magnitude earthquake, according to Germany’s geosciences center GFZ, and it was heard and felt as far away as Cyprus more than 180 miles across the Mediterranean.

Despite Trump’s assertion, the cause of the blast is still not confirmed, but initial reports suggested a fire had detonated a warehouse at the port.

Abbas Ibrahim, chief of Lebanese General Security, said it might have been caused by highly explosive material that was confiscated from a ship some time ago and stored at the port. Local television channel LBC said the material was sodium nitrate. Witnesses reported seeing a strange orange-colored cloud like that which appears when toxic nitrogen dioxide gas is released after an explosion involving nitrates.

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The explosion came amid ongoing tensions between Israel and the Hezbollah military group on Lebanon's southern border. Many residents reported hearing planes overhead just before the blast, fueling rumors of an attack, though Israeli military overflights are common. An Israeli government official said Israel “had nothing to do” with the blast. He spoke on condition of anonymity because he was not authorized to discuss the matter with the news media. Israeli officials usually do not comment on “foreign reports.”

U.S. Secretary of State Mike Pompeo extended his “deepest condolences” to the people of Beirut and said the United States is closely monitoring the situation. “Our team in Beirut has reported to me the extensive damage to a city and a people that I hold dear, an additional challenge in a time of already deep crisis,” Pompeo said in a written statement.

The Associated Press contributed to this report.