California declares state of emergency

California authorities said on Sunday they had discovered a crack in a damaged tank containing toxic chemicals, easing concerns over a potential explosion that prompted the evacuation of about 40,000 residents. The leak began on Friday in Orange County's Garden Grove area, sending fumes across a densely populated region near Disneyland.

1. Frame 1State emergency: Orange County toxic tank triggers evacuations.
2. Frame 2A potential crack may be relieving pressure, but the tank remains unstable.
3. Frame 3About 40,000 residents were told to leave near Garden Grove.
4. Frame 4The tank holds methyl methacrylate, volatile material used to make plastic.
5. Frame 5Crews cool the tank while investigators sort the failure and valve problems.
6. Frame 6The open question: stabilize it safely, or face a spill or blast.