NEW YORK (WPIX) — New York City’s controversial COVID-19 vaccine mandate for all city employees went into effect at midnight.

As of Monday morning, about 9,000 workers – mostly New York Police Department, Fire Department of the City of New York (FDNY) and sanitation employees – refused the order and were put on unpaid leave, according to a spokesperson from the mayor’s office. About another 10,000 remained unvaccinated but were being considered for medical exemptions that would allow them to work and get tested weekly.

Mayor Bill de Blasio said Monday that 91% of the city’s total municipal workforce had gotten at least one dose of a COVID vaccine. That number rose from about 83% on Friday night. Overall, vaccination rates among workers impacted by the mandate increased by 14% over the span of 10 days, according to the mayor’s office.

About 84% of NYPD employees have complied with the mandate. The EMS arm of the FDNY reported an 88% vaccination rate as of Monday morning while the fire portion of the FDNY reported a 77% vaccination rate. The DSNY reported an 83% vaccination rate.

Despite repeated warnings from some unions about slowdowns in service, the mayor insisted the city is safe and response times for 911 calls will not be impacted.

Members of the FDNY firefighters union spoke said Monday that they were not anti-vaccine, but rather, anti-mandate.

The union called the mandate deadline “unconscionable,” arguing that there should have been more time allotted for them to get vaccinated.

However, in a tweet on Saturday, Rep. Nicole Malliotakis said 26 fire companies across the city were closed.

Malliotakis, who represents Staten Island and parts of Brooklyn, said the statistics were provided to her by the Uniformed Firefighters Association union. 

Fire officials clarified fire companies, not firehouses, go out of service. They return to service when resources are moved and additional members are reallocated.

“The department has not closed any firehouses. Irresponsible bogus sick leave by some of our members is creating a danger for New Yorkers and their fellow Firefighters. They need to return to work or risk the consequences of their actions,” FDNY Commissioner Daniel Nigro said in a statement.

In the past week, 2,000 members of the FDNY have been out on medical leave, according to the department. Over half of those on sick leave are unvaccinated, according to FDNY Deputy Commissioner Frank Dwyer.

The Associated Press contributed to this report.