LINTHICUM, Md. - Security screeners discovered a firearm in a carry-on bag at Baltimore's main airport Friday morning and two concourses were closed when its owner could not be found, authorities said. Officials at Baltimore/Washington International Thurgood Marshall Airport held onto the carry-on bag but its owner continued through the checkpoint and could not be located, airport spokesman Jonathan Dean said. "We simply were acting with all due precaution," Dean said. Transportation Security Administration spokesman Christopher White said the bag belonged to a male passenger. He could not be located. Concourses A and B, which serve Southwest Airlines, reopened after 90 minutes. Passengers were being required to go through screening again, Dean said. http://news.yahoo.com/s/ap/20060922/ap_on_re_us/suspicious_package_airport Genius.