3M Co. MMM, -1.64% said Friday it had doubled global production of N95 masks and plans to continue to expand amid concerns about dwindling supplies of the respirator masks for health workers treating COVID-19 patients. The company's output of N95 masks is at an annual rate of more than 1.1 billion a year, 3M said. The company is increasing investments, mostly in the U.S., to expand its global capacity by more than 30% in the next 12 months and maximizing production of other products used to combat the illness, including hand sanitizers, disinfectants and air-filtration products, it said, without providing dollar figures. "3M is working with governments, medical officials, customers and distributors around the world to help get supplies where they are needed most," the company said. The company also warned it had seen more reports of fraudulent and counterfeiting activities involving 3M products. Prices for its products have not changed but 3M said it could not "control the prices dealers or retailers charge for 3M respirators." Shares of 3M fell 5% on Friday, compared with losses around 1% for the S&P 500 index. SPX, -1.11%