Their sister Isabelle died in Thursday's crash, which involved the bus and a dump truck. The triplets' father is New Jersey State Police Sgt. Anthony Tezsla.
Jonathan Zdybel, 11, also was in critical condition at Cooper. His family could not be reached for comment.
State officials reported, meanwhile, that the bus in the Chesterfield accident was a 2012 model-year vehicle that had been inspected in August.
The Tezsla family released a statement through the hospital.
"There are no words to express the gratitude and appreciation that we have for the kindness and professionalism that our rescue workers, doctors and nurses have shown our girls," the family said.
"In addition, the outpouring of love and support that we have received, in particular from everyone in our community and the surrounding communities, has touched us profoundly," it said. "We thank you for your continued prayers for our Isabelle, Sophie, and Natalie."
No charges have been lodged against either driver in the accident, said Joel Bewley, spokesman for the Burlington County Prosecutor's Office.
"It will be a few weeks before the results of the toxicology tests are known," he said Tuesday. Those tests would show whether either driver was impaired.
John Tieman, 66, of Beverly, drove the bus and Michael Caporale, 38, of New Egypt, N.J., drove the dump truck. Both were drivers in good standing at the time of the accident, the Motor Vehicle Commission said.
The bus belonged to Garden State Transport in Southampton. Two hundred and forty-eight of the company's school vehicles were inspected during two visits in October and December.
Thirty-five percent passed, 49 percent were put out of service until repairs were made, and 16 percent were cited for less serious issues and given 30 days for repairs.
