WASHINGTON — The government says drugs were found in the system of about 1 in 5 drivers who were killed in car crashes in 2009, raising concerns about the impact of drugs on auto safety.

White House Drug Policy Director Gil Kerlikowske said today the nation has made progress on drunken driving, but the data show that more research is needed to understand how drugs can affect people behind the wheel.

Government researchers found that drugs were reported in nearly 4,000 drivers who were killed in 2009, or 18 percent of the total drivers killed that year. In 2005, drugs were reported in about 13 percent of drivers killed in car accidents.

Researchers say the numbers could be higher because only about 65 percent of the drivers who died were tested for drugs.