HOUSTON -- The circumstances behind the death of a child who died during a visit to the dentist were released Wednesday, KPRC Local 2 reported.

The Harris County Medical Examiner's Office released the autopsy findings of the death of two-year-old Jessenia Valles, and ruled the death was accidental and not from natural causes.

Valles died from an overdose of an anesthetic commonly used in dental offices called Mepivicaine, officials said.

"The amount that was given resulted in an overdose to the point that contributed to her death," Harris County Chief Forensic Investigator Beverly Begay said.

Investigators said they are not sure who administered the anesthetic.

Valles stopped breathing while having dental work at the Good Shepherd Dental Clinic, located at 6220 Dashwood Drive, in southwest Houston on Oct. 6, her family said.

Her mother was at the office, but said they would not let her in the exam room with her daughter while Dr. Robert Choy repaired cracks in her teeth.

At one point during the examination, she said she heard her daughter crying through the door but was assured she was all right.

Valles was left alone in the exam room for about an hour after the procedure, the mother said. She said a nurse told her that her child needed time to recover.

The mother did not know anything was wrong until a nurse carried Valles out of the exam room unconscious and took her to a doctor's office next door.

An ambulance then transported the girl to Southwest Memorial Hermann Hospital where she was pronounced dead.

The State Board of Dental Examiners warned the dentist in August 2004 that he was not keeping adequate records. That complaint was worked out, officials said.