Federal immigration agents arrested 254 suspected illegal aliens at a City of Industry light fixture assembly plant in what officials said was the largest number of such arrests at once in the Los Angeles area in a decade. The raid involving 36 Immigration and Naturalization officials occurred at the Lights of America plant at 19395 E. Walnut Drive. Officials at the plant refused to comment. Earlier, immigration agents arrested 50 suspected illegal aliens at Atlantic and Beverly boulevards, a “pickup point” where people looking for work can be picked up by employers for a day’s labor, officials said. Of the 304 arrestees, about 10 opted for hearings, and the rest agreed to return to Mexico voluntarily, the immigration service said.