MOSCOW (AP) — Russian authorities have opened a criminal investigation into the deaths of nine babies at a Siberian maternity hospital over the country’s New Year holidays, officials said Tuesday.

The newborns died at Maternity Hospital No. 1 in the city of Novokuznetsk in southwestern Siberia, Russia’s Investigative committee said, confirming that it had opened a case on charges of causing death by negligence.

Most of the babies were premature and all were battling severe intrauterine infections passed between mother and baby, the local health ministry said in a statement carried by Russian news agencies.

It said that 234 children had been born at the hospital between Dec. 1 and Jan. 11, with 17 babies considered to be in a serious condition in the hospital’s intensive care unit.

“Of the 17 infants in a critical condition, 16 of them were premature, including those with extremely low birth weight. All 17 had a severe intrauterine infection,” the health ministry statement said. “Unfortunately, nine children did not survive.”

The hospital’s head doctor, Vitaly Kheraskov, has been suspended from his post while the investigation is ongoing, Gov. Ilya Seredyuk said Tuesday.

The speaker for Russia’s upper house of parliament, Valentina Matviyenko, described the infants’ deaths as not only an irreparable loss for families, but a “tragedy for the state,” which has worked unsuccessfully to boost Russia’s falling birth rate in recent years.

“All of the right lessons must be taken from this tragedy. Conclusions must be made at a federal level. It must never be repeated,” she said in a statement.