(AP) — Amplify Energy’s emergency response plan for a major oil spill like the one unfolding in coastal Southern California depended heavily on a quick shutdown of its pipeline if sensors pick up a sudden loss of pressure.

Federal investigators said Tuesday that's not what happened. They say the Houston-based company waited more than three hours to shut down the pipeline after getting a low-pressure alarm early Saturday.

The alarms also are supposed to trigger immediate follow-up actions to quickly ascertain if anything is wrong.

It’s uncertain why that process dragged out hours in San Pedro Bay, potentially worsening the spill.