A French environmental group is suing the city over widespread lead dust contamination released in the historic cathedral fire on April 15.

Three months after the devastating fire at Notre-Dame Cathedral in Paris, reports of a new, previously unheeded threat to local residents have emerged: lead poisoning. According to confidential documents leaked to the (paywalled) website Mediapart earlier this month and discussed across French media, locations surrounding the fire-damaged cathedral have registered levels of lead contamination ranging between 500 and 800 times the official safe level. The building’s roof and spire were clad in several hundred tons of the metal, which can be toxic if particles are inhaled or consumed, especially to children. The blaze that consumed the cathedral’s roof liquified oceans of lead and lofted a plume of lead particles across the city.

This month’s lead alert has triggered the indefinite closure of two local schools and a halt to all work on the cathedral site. Yesterday, the French environmental NGO Robin Des Bois announced that it will take the city of Paris to court, accusing it of neglecting public health and even of “deliberate endangerment of people.” The dispute raises some troubling, and not yet fully answerable questions. Why did the city not reveal the possible public health dangers related to the fire sooner? And exactly how badly has the region been contaminated?