A Houston doctor is under investigation on charges that he performed illegal late-term abortions after former employees alleged that several babies were born alive and then killed in gruesome ways.

Deborah Edge, a former assistant to Dr. Douglas Karpen, gave her account of Karpen's abortion work in a video produced by the pro-life group Life Dynamics.

"When he did an abortion, especially an over 20 week abortion, most of the time the fetus would come completely out before he either cut the spinal cord or he introduced one of the instruments into the soft spot of the fetus in order to kill it ... or actually twisting the head off the neck with his own bare hands," she said.

Edge emphasized that the babies were still alive, moving and breathing. Another former employee in the video, Gigi Aguliar, said one baby opened its eyes and grabbed the abortionist's finger before he killed it.

One employee said she did not know what Karpen was doing was illegal.

The allegations concern deaths in 2011 at the Aaron Women's Clinic in Houston. A third former employee appears in the Life Dynamics video, while another anonymous staffer has filed an affidavit Texas Department of State Health Services, the Daily Mail reports.

The former employees took cell phone pictures of babies with gashes in their necks after they were allegedly killed at the clinic, LifeNews.com says. They allege that Karpen killed babies well after 24 weeks into pregnancy, at a cost between $4,000 and $5,000.

Karpen also runs two other abortion clinics in Texas.

Texas Lt. Gov. David Dewhurst said he read "with disgust" about the allegations that Dr. Douglas Karpen performed "illegal late-term abortions surrounded by appalling sanitary conditions in his clinic."

"The Harris County authorities should perform a full-scale investigation and take action against those who broke state law," he said in a May 15 statement.

Sara Marie Kinney, a spokeswoman for the Harris County District Attorney, said several district attorney employees are looking into the allegations.

Carrie Williams, a spokeswoman for the Texas Department of State Health Services, told the Houston Chronicle the agency is aware of the allegations and investigating it with "a very high priority."

Dewhurst invoked the case of Kermit Gosnell, a Philadelphia abortionist convicted last week on three charges of first degree murder for killing babies who survived abortions.

The pro-life group Operation Rescue has said it has been investigating Karpen for three years.

"For nearly three years, authorities have ignored our complaints and done nothing while horrific late-term babies continued to be aborted in an apparently illegal and barbaric manner," group  president Troy Newman said May 16.

"Now, thanks to the outpouring of public pressure that has been brought to bear by the pro-life community, the authorities in Texas are finally beginning to act. It's a big step in the right direction."