Officials say it was arson that caused an enormous fire that damaged a stretch of the I-10 Freeway near downtown L.A., shutting it down to traffic. The closure has made L.A.’s already terrible congestion even worse for commuters across much of the city. State transportation officials say they’re working around the clock to speed the reopening of the 10 Freeway. But they acknowledge they face a difficult challenge and have no idea when the repairs will be finished.