Several people have been found dead at a home in Pike County, Ohio, officials said.
Eight people have been killed, including children, at three different crime scenes, local media reported. Those killed are members of the same family, CBS 6News claimed, but did not cite the source of the information.
The Ohio Bureau of Criminal Investigation's crime scene search unit and cyber crimes unit were heading to the scene about 75 miles (120 km) east of Cincinnati, the Ohio Attorney General's office told Reuters.
All Adams County Ohio Valley schools are on lockdown, school officials told 12KSLA News.
No-one had been arrested and they were not aware of an "active shooter" situation, Dan Tierney, spokesman for the Ohio Attorney General, said, as quoted by the BBC. The Attorney General's office provided no confirmation of the number of people killed or how they were killed.
Ohio Governor John Kasich and Republican presidential candidate described the situation as "tragic beyond comprehension" in a tweet.