The New York State Nurses Association says three Mount Sinai labor and delivery nurses were "unlawfully terminated" and 14 others were disciplined the night before what became the largest nursing strike in New York City history.

The battle cries from 15,000 nurses who are demanding a fair contract only grew louder, as the strike entered Day 2.

“We’re on a legally protected strike," said Lisa Gehrung, a nurse at Montefiore. "We’re willing to stay here for as long as we need.”

Mount Sinai at first denied that the nurses were terminated.

“In this situation, these three nurses were disciplined, not fired after their own co-workers complained about them actively interfering with other nurses providing patient care in the emergency department,” a hospital spokesperson previously said.

Mount Sinai later walked back their statement, telling News 12 they were fired for "interfering with patient safety."

The private hospital alleges these nurses "deliberately sabotaged" emergency preparedness drills ahead of NYSNA’s strike, including hiding supplies from agency nurses who were in training so that they were prepared to help Mount Sinai continue to deliver patient care.

"This is completely unacceptable behavior, which included locking critical supplies designed to care for vulnerable newborns in conference rooms where they did not belong," a spokesperson for Mount Sinai said.

The same spokesperson said the accused health care workers lied about their involvement but were "easily refuted by reviewing security footage of the incident."

NYSNA was not immediately available to respond to these allegations.

The strike comes as talks between NYSNA and Montefiore, New York-Presbyterian and multiple Mount Sinai hospitals collapsed when contracts expired in December. Nurses say they are demanding safer working conditions, protection from workplace violence and improved staffing levels to better care for patients.

Montefiore disputes the union’s demands, telling News 12 that meeting them would cost the health system an estimated $3.6 billion, including a proposed 40% wage increase. The hospital also raised concerns about what it called “troubling proposals” – including limits on terminating nurses found to be impaired by drugs or alcohol while on the job.

Mount Sinai officials said just under 20% of their nurses reported to work on the first day of the strike and expect similar staffing levels Tuesday, as nurses also fight for better healthcare.

The union says hospitals are looking to cut their health care plans, but Sinai tells News 12 this is false.

"The hospital only controls whether it agrees or doesn’t agree to be part of the NYSNA health plan under one of its coverage offerings,” the hospital wrote in a statement. "We do not even have the ability to make changes to the plan for just our employees."

Montefiore and Mount Sinai are spending millions of dollars to bring in temporary nurses to ensure patient care is not disrupted during the walkout. The strike is expected to continue as negotiations remain at a standstill.