MAPLEWOOD, Minn. (AP) — 3M Co. is stepping up production of respirator masks as worries grow about the threat of swine flu. 3M spokeswoman Jacqueline Berry says the Maplewood-based company has seen an increase in global demand, and it's increased production, adding more shifts and manufacturing lines. Reports from Mexico, where swine flu has hit hard, have shown people wearing cloth masks or thin, paperlike dust masks often used on construction sites. But the Food and Drug Administration suggests respirators labeled "N95" for the best protection. Last year, two 3M models — the 8612F and the 8670F — became the first respirators cleared by the FDA for use in public health emergencies.