Two of the six power units that had collapsed in Kolaghat on Tuesday were revived this evening, but the districts still stayed dark because generation was low. The 210MW units had collapsed after the switchyard of the Kolaghat thermal power plant got flooded. Six pumps helped clear the water in the switchyard. "But there was a thick layer of slush in the switchyard which had to be cleared. This led to delay in repairs,' a power department official said.