The deaths of eight family members — including six children found in a burning Oklahoma home — are being investigated as a murder-suicide, authorities said Friday. Police are trying to determine whether both adults were involved in the killings.

The children, who ranged in age from 1 to 13, were the victims, Broken Arrow Police Chief Brandon Berryhill said during a news conference. He did not provide their identities, ages or explain their relationships to one another except to say they were family members believed to be living in the home.

Police said both adults who live in the home were con...