Parents of three-year-old Daleyza Avila Hernandez of Stockton, California are in shock after their daughter died during a simple dental procedure on 12 June. They are clueless about what went wrong in the dentist's clinic that led to her sudden death.

"All I did was I took my daughter to the dentist because they were going to fix her teeth, and about 30 minutes later they brought her back dead," Araceli Avila, Daleyza's mother, told Fox40 news channel in Spanish.

The girl's parents are demanding answers from the dental clinic. Doctors suspect the death could be because of some underlying heart ailment the girl might have been suffering from. However, the parents say their daughter was healthy. They now want the dental centre to be shut down, and took out a vigil on Friday (16 June) to press for their demands.

"I don't want this to happen to another mother like it's happening to me," Avila said.

She said that a dentist at Western Dental referred her daughter to the Children's Dental Surgery in Stockton, where she was supposed to have two teeth pulled and caps put on two other teeth. Sharing her daughter's photos, the grieving mother said she was not allowed inside the surgery room, but a while later she saw an ambulance parking outside the centre.

"And I stood up and went outside because I was like 'they are coming for a kid,' but I never thought it was for my child," she said.

David Thompson, the administrator of the Stockton centre, told the news channel that the child had a reaction to the anesthetics during the dental procedure on Monday (12 June).

She was stabilised and then sent to Saint Joseph's Hospital, Thompson said, adding that they too have no clue why the girl died. "It's a terrible, terrible tragedy honestly and our thoughts and prayers are really with the family right now."

The Dental Board of California released the following statement, saying that an investigation is underway to find out the cause of the girl's death. The Stockton Police Department has also launched a probe.