( CNN ) -- Three of the seven victims of a highway attack this week in the Mexican state of Veracruz were American citizens , officials said . A mother and her two daughters , dual Mexican-U.S. citizens who lived in Fort Worth , Texas , were aboard one of three buses that were attacked by gunmen in the city of Panuco , in the northern part of Veracruz . `` We express our deepest condolences to their family and friends during this difficult time , '' State Department spokeswoman Neda Brown said . A Mexican official in the state of Hidalgo , the hometown of the mother , identified the Americans as Maria Sanchez Hernandez and her two daughters , Karla , 19 , and Cristina , 13 . The buses were on a road between the towns of Tempoal and Panuco near the border of Veracruz and Tamaulipas , Mexican and U.S. government officials said . CNN.com : More violence in Veracruz . An American consulate general statement warned American citizens to `` exercise caution and remain vigilant when traveling in the state of Veracruz . American citizens residing in , visiting or traveling through the northern portion of Veracruz that borders Tamaulipas and San Luis Potosi should maintain a heightened sense of alert . '' Inter-city road travel at night should be avoided , the consulate general said . CNN 's Mariano Castillo and CNNMexico.com contributed to this report .
Seven people were killed in a highway attack this week . The Taliban claimed responsibility for the attack, which occurred on Saturday near Kandahar city, but it was unclear if they had been behind it.