NEW YORK (AP) - The bridge that collapsed in the Italian port city of Genoa was considered a feat of engineering innovation when it was built five decades ago, but it came to require constant maintenance over the years.

Its design is now being investigated as a possible contributor to its stunning collapse. The Morandi Bridge was severed in its midsection during a heavy downpour Tuesday, killing at least 39 people. Italian prosecutors focused their investigation on possible design flaws or inadequate maintenance of the 1967 bridge.

Engineering experts said the disaster points to the challenges of maintaining any aging bridge, regardless of its design.