Firefighters were called to the Wastewater Treatment Plant at Sand Island at about 2 a.m. Tuesday for a two-alarm fire. Hawaii News Now is reporting that a tank was undergoing routine maintenance and a residue leaked out, then caught fire. No one was injured and there were no evacuations. The flames were extinguished about an hour later and the crews left the scene by about 4 a.m. Plant officials will assess the tank to see if operations will be affected.