BEIRUT — An explosion Tuesday at a Hezbollah-linked facility in southern Lebanon sent black smoke billowing from a leveled building, footage from the area showed.

Members of the Iran-backed Hezbollah group cordoned off the area around the blast site in the village of Ayn Qana, according to a source linked to the armed group. They spoke on the condition of anonymity because of the sensitivity of the issue. It was unclear whether anyone had been killed or wounded.

Lebanon’s state National News Agency said that the blast had coincided with “intensive” traffic from Israeli aircraft, but that the cause of the blast was unknown. It comes as Lebanon is reeling from a huge explosion at Beirut’s port Aug. 4, which destroyed surrounding neighborhoods, killed almost 200 people and injured more than 6,000. An investigation is still underway into the initial cause of a fire which ignited 2,700 tons of ammonium nitrate stored at the port.

A string of subsequent fires and explosions has kept the country on edge since then, including a small fire at Tripoli’s port and one at a paint factory in Beirut’s southern suburbs Tuesday.

The Ayn Qana explosion, however, appeared to be the first involving a site linked to Hezbollah, raising the possibility of sabotage.

It coincides with heightened tensions along Lebanon’s southern border with Israel, after Hezbollah vowed to retaliate for the killing of a Hezbollah operative in Syria in July. On at least two occasions, Israeli troops have opened fire on what they claimed were Hezbollah operatives attempting to infiltrate the border. Israeli warplanes have also intensified their surveillance flights across Lebanon, contributing to the jumpy mood here.

Israel has long threatened to strike at Hezbollah weapons sites in Lebanon, but there has been no evidence that any of the unexplained fires and explosions in recent weeks have been anything other than accidental.

There were echoes in this incident of a string of initially unexplained explosions at weapons storage facilities across the region, including earlier this year at Iranian power plants and military sites, which intelligence officials have since attributed to Israeli sabotage.

Sly reported from Istanbul. Suzan Haidamous in Washington and Sarah Dadouch and Nader Durgham contributed from Beirut.

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