(NEWSER) – Clues to what may have caused the Asiana Airlines crash this weekend continue to emerge. The latest: The plane's pilot said that while flying at 500 feet, he was blinded by light, investigators say. "It was a temporary issue," says National Transportation Safety Board chair Deborah Hersman, but its cause remains uncertain. "We need to understand exactly what that is," she says, perUSA Today. She also discussed the plane's apparently delayed evacuation.