PARIS (AP) — A massive fire engulfed the upper reaches of Paris' soaring Notre Dame Cathedral as it was undergoing renovations Monday, threatening one of the greatest architectural treasures of the Western world as tourists and Parisians looked on aghast from the streets below.

The blaze collapsed the cathedral's spire and spread to one of its landmark rectangular towers, but Paris fire chief Jean-Claude Gallet said the church's structure had been saved after firefighters managed to stop the fire spreading to the northern belfry. The 12th-century cathedral is home to incalculable works of art...