Five infants suffered serious injuries ‒ including a fractured skull, rib and arm ‒ in the newborn intensive care unit of a Wisconsin hospital, resulting in the suspension of the nurse who cared for them, a federal agency said in a report.

UnityPoint Health-Meriter hospital in Madison didn’t respond to the suspected abuse until early last month, when staff noticed two babies with bruises, the Wisconsin State Journal reported.

An internal investigation revealed two similar cases last year and one in January.

The Center for Medicare and Medicaid Services was so concerned about the hospital’s response that it threatened to cancel its Medicare contract with Meriter, the newspaper said, citing a report from the federal agency.

"The immediate jeopardy began on April 12, 2017 when the facility failed to protect and thoroughly investigate the first report of an injury of unknown origin" to one of the patients, the report said, according to WISC-TV.

Staff in the 42-bed unit first noticed bruising on an infant's arm on Feb. 2, according to the inspection report. A doctor thought it might have resulted from the baby clutching wires or an IV device.

The next day, staff noticed bruising on an arm and wrist of another baby. A doctor thought it might be from a tightly wrapped blanket.

Staff then saw additional bruising on the second baby’s face on Feb. 4, and three days later they discovered a lump on the baby’s head. A CT scan on Feb. 8 showed the baby had skull and arm fractures.

The federal agency told Meriter in a Feb. 23 letter that the situation “is so serious that it constitutes an immediate threat to patient health safety,” and that the Medicare program will not make payments for patient services on or after May 24, the station reported.

The agency determined that the hospital failed to “develop and implement effective policy to prevent suspected abuse related to injuries of unknown origin for patients in the Newborn Intensive Care Unit,” WMTV-TV reported.

The identity of the suspended nurse has not been released.

The Madison Police Department is investigating.

Meriter spokeswoman Jessika Kasten said the hospital is cooperating with authorities and has implemented new safety measures, telling the federal agency that it has assigned a security guard to the newborn unit and is putting cameras in all rooms.

Each nurse will also now care for two patients instead of three in the unit, which handles babies in intensive care.

The Associated Press contributed to this report.