Japan’s nuclear safety and industrial agency reported sounds of an explosion at the Fukushima Daiichi nuclear plant’s No. 3 reactor, according to Japanese public broadcaster NHK.

White smoke could be seen rising from the facility at 11 a.m. Monday.

Workers have been flooding this reactor and the plant’s No. 1 reactor with seawater to cool them after the earthquake and tsunami damaged the reactors’ cooling systems.

Chief Cabinet Secretary Yukio Edano said a day earlier that accumulating hydrogen gas “may potentially cause an explosion” in the building housing the No. 3 reactor at the Daiichi plant. A similar scenario played out Saturday, when a blast caused by hydrogen buildup blew the roof off a concrete building housing the plant’s No. 1 reactor. The reactor and its containment system were not damaged in the explosion at the No. 1 reactor.

(Source: CNN)