Summary:
A tsunami warning is in effect for the eastern US, but the cause of the wave is still unclear.

Full article:
(CNN) -- Scientists are studying what caused tsunami-like waves that observers spotted near the New Jersey coast earlier this month. "The source is complex and still under review," the National Weather Service's West Coast/Alaska Tsunami Warning Center says on its website. In New Jersey's Barnegat Inlet, a fisherman said he saw a massive, 6-foot-tall wave surging toward the coast on June 13. Tsunami-like waves were observed at more than 30 tide gauges in areas along the East Coast, the center said. Meteorological factors and the slumping of the continental shelf east of New Jersey may have played a role, the center said.