France's Culture Ministry says several stones fell from the vaulted ceiling of the fire-ravaged Notre Dame Cathedral after last month's heat wave, and is urging renewed stabilization efforts to prevent further damage.

A ministry official said Wednesday that the stones fell after temperatures reached a record 42.6 Celsius (108.7 Fahrenheit) in Paris in late July. The official said the heat quickly dried out the mortar holding ceiling stones in place and apparently played a role.

The damage is "not serious" but the 12th-century cathedral remains at risk of possible collapse, the official said. The official was not authorized to be publicly named according to ministry policy.

Work inside the cathedral was suspended over concerns about lead contamination. The ministry urged resumed efforts to clean out hazardous debris and shore up the structure, severely damaged in the April fire.

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