PASSAIC, N.J.—A massive fire engulfed a northern New Jersey recycling plant overnight and raged into Saturday as firefighters battled flames, frigid cold, and wind. Officials warned it could burn for days. The blaze broke out around midnight at the Atlantic Coast Fibers plant in Passaic, sending flames shooting into the dark as more than two dozen fire departments converged to fight them, officials said. There were at least two explosions, one involving a truck with gas tanks on it, Mayor Hector Lora said. Smoke continued to billow high into the sky after sunup, and Lora said firefighters were planning to tap the Passaic River for water to keep dousing an inferno that could take days to extinguish completely. “When you consider a recycling plant, everything inside is conducive for continuing to burn,” he told WABC-TV in a phone interview, calling the building “a complete loss.” The flames erupted on a …