The 787 has two identical lithium-ion batteries, one of which is located toward the front of the plane and powers cockpit electrical systems, the other toward the rear and used to start an auxiliary power unit while the plane is on the ground, among other functions.

NPR: FAA Approves Resumption Of Boeing 787 Flights

The main investigation, which also involves the FAA and Boeing, focuses on the 787's cutting-edge lithium ion battery system that powers the plane's auxiliary power unit.

CNN: Quick fix for Dreamliner looks less likely, experts say