The US military said Friday it was investigating reports of a US helicopter going down north of Baghdad. The statement came after police and witnesses reported that at least one helicopter had been shot down Friday in the area surrounding Taji, an air base 20 kilometers (12 miles) north of the capital. Some witnesses described two helicopters going down. "I can confirm that we are looking into reports that a helicopter went down north of Baghdad," US military spokeswoman Lt. Col. Josslyn Aberle said. Police and witnesses said the area had been sealed off by American forces and US planes were flying overhead.