MONTERREY, Mexico -- A shopping mall under construction in the Mexican city of Monterrey collapsed Thursday, killing at least seven people and leaving another nine missing, officials said.

Local council secretary Genaro Garcia told a news conference 15 people were injured, in addition to the dead, and all the victims are believed to be construction workers.

Work on the three-story structure in this northern industrial hub in Nuevo Leon state was being carried out without the necessary license, authorities said.

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The concrete slabs of the structure appear to have pancaked, falling one atop another. Images taken by civil defense officials showed emergency personnel hauling the injured men out of the rubble. About 150 emergency personnel were looking for more people who may be trapped.

Late Thursday night, the civil defense office released a brief statement saying nine people were still missing.

In July, a newly opened shopping mall on the south side of Mexico City partially collapsed. A support beam at the Artz Pedregal mall failed, enabling operators to evacuate the mall so no one was injured when the top floors collapsed about five minutes later. Parts of the mall were under construction even though it opened in March.