Complex sentence: At first, officials feared that the wire itself--which is over 1,000 feet long and weighs several tons--had snapped, which would have taken several weeks to manufacture and install a replacement.
Split into simpler sentences: At first, officials feared that the wire itself--which is over 1000 feet long and weighs several tons--had snapped. If the wire had snapped, it would take several weeks to manufacture and install a replacement.