Under intense questioning from reporters, officials with the Centers for Disease Control and Prevention (CDC), the Texas health department and the City of Dallas repeatedly declined Thursday to provide details about the steps being taken to prevent an outbreak.

Texas Health Commissioner David Lakey, who participated in one press call Thursday, would not identify or describe the four individuals who have been quarantined due to possible exposure to Ebola. They were later referred to as “family members” at a separate press conference.

Officials confirmed that roughly 100 people are being questioned about possible exposure to the virus. Only a “handful” likely could have caught it, and no one but the patient is showing symptoms, they said.

Neither would Lakey explain why the quarantine order was necessary, saying only that it brings “confidence” that key medical monitoring will take place.