A crack in a tank holding a toxic chemical may have helped avert an explosion or bigger leak, as evacuation orders begin to lift.

California officials have lifted the final remaining evacuation orders in Orange County after securing a chemical tank leak, allowing Garden Grove residents to return to their homes after a week of nerves over the possibility of a spill or explosion.

Evacuation orders have lifted after the Garden Grove chemical scare, but GKN Aerospace now faces class-action lawsuits and questions over negligence that displaced roughly 50,000 residents for days. The Garden Grove plant is a rare global supplier of fighter-jet canopies and airliner windows.

About 40,000 people are under evacuation orders and schools have shut down in Southern California due to a hazardous chemical leak.

An official said there's no active leak, but evacuations orders are to prepare for either a spill or an explosion from a failing chemical tank.

Two emerging factors may be helping reduce the risk of a catastrophic explosion at the chemical tank in Garden Grove, California.

The risk of a catastrophic explosion of a damaged chemical tank Southern California has been eliminated following a close overnight inspection that confirmed a crack in the tank has relieved pressure and cooled the chemical.