WASHINGTON (AP) — A U.S. official says investigators are examining the possibility that someone caused the disappearance of a Malaysia Airlines jet with 239 people on board, and that it may have been "an act of piracy."

The official wasn't authorized to speak publicly on the matter and spoke only if not identified. While other theories are still being examined, the official says key evidence for "human intervention" in the plane's disappearance is that contact with its transponder stopped about a dozen minutes before a messaging system quit.

This official says that it's also possible the plane may have landed somewhere.

Another communications system on the plane continued to "ping" a satellite for about four hours after contact was lost with the Boeing 777 during a flight from Kuala Lumpur to Beijing — an indication the plane may have continued to fly on for hours.