OMAHA, Neb. — The parents of an infant killed last year by his nanny filed a lawsuit Thursday against the woman and her former employers, saying the child care facilities failed to report allegations that the nanny previously had been abusive to children in her care.

The lawsuit, filed by Christopher and Ashley Bell, of Omaha, in Douglas County District Court, names as defendants the nanny, Sarah Cullen; Grow With Me child care and its former director, Jennifer Schmaderer; La Petite Academy child care and its former director, Lisa Hampson; and online family care service Care.com.

A woman who answered the phone at Grow With Me child care declined to comment on the lawsuit. A message left Friday Care.com was not immediately returned. Neither Schmaderer nor Hampson could be reached for comment.

A spokeswoman for La Petite's parent company, Learning Care Group Inc., said Friday that officials there had not seen the lawsuit and could not comment on it.

Cullen is serving a prison sentence of 70 years to life for causing injuries in late February 2013 that killed 4-month-old Cash Bell. Doctors said the baby had sustained severe head trauma, including multiple skull fractures and hemorrhaging that indicated he had been violently shaken.

In April, Cullen's former boss, Schmaderer, was found guilty of a misdemeanor count of failing to report suspected child abuse by Cullen. She faces up to three months in jail and a $500 fine when she is sentenced in July.

The Bells' lawsuit says they used Care.com in late 2012 to help them find a nanny. The online service offered a free search option or a paid monthly membership that included background checks on nanny candidates. The Bells opted to pay the membership fee in order to use the criminal background checks.

Care.com provided the Bells with about 30 candidates, the lawsuit says, and the Bells narrowed that to two — Cullen and another woman — based on previous child care experience and other criteria.

The Bells selected Cullen and asked Care.com to perform a background check on her. The background report said that no criminal cases against Cullen were found, despite her drunken driving conviction in June 2012.

The Bells say they would not have hired Cullen if they had been made aware of her conviction.

"Our son Cash's death is a tragedy that could have been prevented," the Bells said in a statement. "It is our sincere hope that by filing this civil lawsuit against those responsible for Cash's death, we can raise awareness of infant child abuse and prevent other young children from suffering the same fate as Cash."

The lawsuit also says Hampson and Schmaderer failed to report suspected child abuse at the hands of Cullen while she worked at their facilities, and that Schmaderer covered up the allegations of abuse by lying to parents about their children's injuries.

The lawsuit claims Cullen had violently flung toddlers to the ground and once shoved a baby shoe into the mouth of a 14-month-old, splitting the baby's lip.

La Petite spokeswoman Lydia Cisaruk said the matter first came to the company's attention last fall and that the "situation is very upsetting."

"As regulated caregivers, we take our responsibility to meet or exceed state guidelines seriously," Cisaruk said. "We have strict policies and procedures to ensure that we're providing the highest level of care."

The lawsuit is seeking an unspecified amount for medical, funeral and burial expenses, Cash's pain and suffering and other damages.