Nine young and impoverished Afghan girls lost their lives in a land-mine explosion Monday while they were collecting firewood in eastern Afghanistan, officials said.

The blast, outside a village in the Chaparhar district of Nangarhar Province, left three other girls wounded. All the victims were schoolchildren, between 9 and 11 years old, according to information provided by government officials.

The provincial governor’s office initially said 10 girls were killed by the land mine, and two injured. But officials later revised the number of fatalities to nine, with three injured.

The governor’s office did not say whether the land mine was an old one left over from the Afghans’ war against Soviet invaders, or a new one planted in the current conflict between Taliban-led insurgents and foreign troops led by the United States.

Roadside bombs and land mines kill or maim scores of Afghan civilians monthly in Afghanistan. The devices are the main cause of casualties among foreign troops.

In a separate incident in Kabul, a suicide bomber blew up a vehicle laden with explosives outside the offices of Contrack, a McLean, Va.-based firm located near military bases used by foreign forces in Afghanistan’s capital.

At least 15 people were wounded, most of them Afghan workers at the firm, Kabul’s deputy police chief Daoud Amini said.

The powerful blast was heard across the city, sending a plume of smoke up in the air and causing damage to the company’s compound, witnesses said. A Taliban spokesman said the group was behind the attack that targeted Contrack.

Also Monday, the U.S. Embassy in Kabul issued a warning to American citizens in the country reminding them to be cautious about their movements. The embassy did not say if the warning was linked to the attack on the firm or if it came as a result of another possible threat.