The U.S. National Transportation Safety Board has launched a major investigation into the alleged use of a cell phone in a traffic accident over the weekend in Washington D.C. in which five people were killed.This is the first time the agency has conducted an in-depth probe into the possible role of a cell phone in a crash. The agency has begun to check for mobile phone use in investigations, following a fatal traffic accident in Illinois recently in which the driver believed to be responsible was talking on the phone, according to an NTSB official.Cell phone use has recently been cited as a contributing factor in a number of other traffic deaths. The Board may issue recommendations on vehicular cell phone use after completing a report later this year.The National Highway Transportation Safety Administration (NHTSA) is in the midst of an investigation into how cell phones and other digital communications devices distract drivers. The State of New York, along with several municipalities around the United States, have outlawed talking on portable phones while driving. Other states are considering following New York's lead.The Cellular Telecommunications & Internet Association has said it opposes laws that forbid drivers from talking on cell phones while driving. The trade group emphasizes education.