MARSEILLE, France — Two buildings collapsed into a pile of rubble and beams Monday in the French city of Marseille, where authorities spoke of a race against time to find people possibly trapped in the ruins.

The buildings — one condemned and supposedly vacant, the other containing apartments — gave way after 9 a.m. In the spot where they had stood, a large gap appeared once the dust and debris settled.

Marseille fire services said two people who were in the street when the buildings collapsed were treated for light injuries. French President Emmanuel Macron said Monday evening it was unknown if anyone was killed or trapped.

Fire officials deliberately brought down most of a third building due to concerns the unstable structure might cave on top of search crews and sniffer dogs combing the rubble of the other buildings. The late afternoon demolition released more dust clouds.

Authorities said one building had been condemned as substandard and was assumed to be unoccupied, but the other was inhabited. The government's housing minister, Julien Denormandie, said at the scene he couldn't rule out that people were trapped in the collapse.

"It's a race against the clock," Denormandie said. "The urgent task is to determine whether there are people we can save."

Thick dust covered cars around the site near Marseille's famous Old Port. Amateur video broadcast on BFM-TV featured bystanders covering their mouths with their sleeves to avoid the dusty air.

Images of the buildings before they collapsed, visible on Google Street View , showed that one had five floors and the other six.

One of the buildings was clearly in poor repair, with boarded-up windows and large visible cracks on the facade before it collapsed.

Sabine Bernasconi, the local mayor for that part of Marseille, said one of the buildings was subject to an evacuation order, but could not say for sure that squatters were not using it.

The regional prefecture urged people to avoid the area and make way for emergency services.