MEXICO CITY (AP) — As many as 50 people in Mexico are missing after they set off on simple highway trips between the industrial hub of Monterrey and the border city of Nuevo Laredo. Relatives say they simply disappeared on the heavily traveled road, which local media has dubbed ‘the highway of death,’ never to be seen again. The highway disappearances this year, and last week’s shooting of 15 innocent bystanders in Reynosa, suggest Mexico is returning to the dark days of the 2006-2012 drug war, when drug cartel gunmen often targeted the general public. Six the victims are believed to be U.S. citizens or residents.