ANDERSON, Ind. (AP) — Police have arrested the grandfather of a mentally disabled 15-year-old girl who was taken to an Indianapolis hospital weighing less than 40 pounds.

Anderson police Detective Joel Sandefur says the girl is in critical, life-threatening condition Tuesday and cannot speak to investigators. A probable cause affidavit says a nurse was using a device to help the girl breathe when police arrived.

Authorities jailed the girl’s 58-year-old grandfather Monday on a preliminary charge of neglect of a dependent.

Sandefur says no court hearing is set, and that the man, who says he is the girl’s legal guardian, is being held while the investigation continues. He didn’t know whether the man has hired an attorney.

Sandefur says the grandfather blamed the girl’s low weight on an unspecified medical condition.