RABAT, Morocco (AP) — Two four-story buildings collapsed overnight in the Moroccan city of Fez, killing 22 people in the second fatal collapse there this year, authorities said on Wednesday.

MAP, Morocco’s state news agency, reported the two residential buildings housed eight families. Sixteen people were injured in the collapse and taken to the hospital. Authorities said the neighborhood had been evacuated and search and rescue efforts were ongoing.

It was unclear what caused the collapse or how many people were unaccounted for on Wednesday morning, but authorities said an investigation had been opened. MAP reported that the structures were built in 2006 during a self-construction initiative called “City Without Slums.”

Fez is Morocco’s third-largest city and one of the hosts of this month’s Africa Cup of Nations and the 2030 FIFA World Cup. It is best known for its walled city packed with medieval souks and tanneries. But beyond tourism, it’s also one of the country’s poorest urban centers, where aging infrastructure is common in many neighborhoods.

Such collapses are not uncommon in Moroccan cities undergoing rapid population growth. In Fez, a collapse in May killed 10 people and injured seven in a building that had already been slated for evacuation, according to Moroccan outlet Le360.

Building codes are often not enforced in Morocco, especially in ancient cities where aging multifamily homes are common. Gaps in basic services were a focal point of protests that swept the country earlier this year, with demonstrators criticizing the government for investing in new stadiums instead of addressing inequality in health care, education and other public services.

Note: A previous version of this story called Fez Morocco’s second-largest city. It is Morocco’s third most populous city.