CHICAGO -- Boeing engineers investigating problems with the new Dreamliner 787's batteries say the short circuits might have been caused by metal whiskers.

Boeing's new fleet has been grounded in several countries pending results of the investigation.

According to the Wall Street Journal, officials are looking at whether dendrites formed on the jet's lithium-ion batteries and whether those whiskers either grew together or arced, causing a short that led to incidents on several planes.

At least one 787 caught fire following a short circuit, but the investigators have yet to conclude whether the dendrites were the source. Previously, Boeing vice president and 787 chief project engineer Mike Sinnett said the fault had been traced to the printed circuit boards.

The incidents recall problems with sudden unintended acceleration in several Toyota vehicles. In that case, NASA investigators found significant evidence of tin whiskers but their final report was sanitized by the US National Highway and Transportation Safety Administration.

Click here to link to a Wall Street Journal rendering of the 787 battery wiring. And here's a white paper from Texas Instruments on battery circuit architecture.