The US military said Wednesday that it was investigating an Afghan news report that a coalition operation may have left more than two dozen civilians dead. Two Afghan officials said a government investigation found only militants were killed. Afghan President Hamid Karzai has long urged US and NATO troops to avoid civilian casualties. The deaths could undermine his re-election bid this year, and also erode support that the foreign forces need to help Karzai's government extend its reach across the country. On Tuesday, the coalition said a nighttime raid had killed 19 militants, including a locally feared leader, during an operation in the Tagab Valley, a militant hotbed in Kapisa province just 50 kilometers north of Kabul. US spokesman Col. Greg Julian said in a statement Wednesday that a coalition investigation would work to "determine the truth" after the Afghan news agency Pajhwok quoted villagers who said 25 civilians had been killed.