An investigation by The Wall Street Journal found that thousands of buildings across the United States and around the world are wrapped in the same exterior panels that fueled the deadly fire in London’s Grenfell Tower. Typically made of polyethylene, these panels are highly combustible and safety experts warn that they shouldn’t be used in high-rise buildings where it’s difficult for fire ladders to reach.

Still, in 2009, at the request of a panel manufacturer, the body that issues fire-safety guidelines in the U.S. recommended loosening codes to allow these panels to be used at any height.