(NBC NEWS) — At least 414 people were killed and almost 6,500 others injured after a 7.3-magnitude earthquake struck near Iran’s border with Iraq, authorities said Monday.

Rescuers were trying to find survivors trapped under collapsed buildings but their efforts were hindered in many places by landslides. More than 100 aftershocks were registered, according to Iranian officials.

Many houses in rural areas of Iran are made of mud bricks that can crumble easily in a quake.

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