NEW YORK — The Metropolitan Transportation Authority suspended subway service on the B, W and Z lines Thursday due to staffing shortages brought on by the recent surge in COVID-19 cases.

The MTA briefly listed Z train service as being restored in the evening, but the MTA's website listed Z train service as suspended again by 6:15 p.m.

In a series of tweets, the agency said, "Like everyone in New York, we've been affected by the COVID surge. We're running as much train service as we can with the crews we have available."

For B train riders, the MTA suggests using Q trains in Brooklyn and D trains in Manhattan and the Bronx as an alternative.

W train riders can use an ‌N‌ train in Queens or an ‌R‌ train in Manhattan.

For the latest updates, visit mta.info.

In a tweet sent out Sunday, the MTA said trains would run less frequently from Monday through Thursday.

It was unclear how many MTA workers were out due to the fast-spreading omicron variant at the time.

The service suspensions come as five new pop-up testing sites are set to open Thursday inside several subway stations around the city.

The MTA began offering walk-in testing and vaccinations at Times Square and Grand Central on Monday. 

The state is now expanding its testing program to several other locations across the borough Thursday. 

Free PCR tests will be available at Penn Station in Manhattan, Broadway Junction in Brooklyn, and East 180th Street in the Bronx. 

In Queens, two stations will offer testing including Roosevelt Avenue and Jamaica 179th Street. 

Penn Station does not open until 3 p.m.

The other stations open at 8 a.m.

The sites will be open Monday through Friday except Penn Station which will be open through Sundays. 

They will all be closed on New Year's Day. 

State officials say the pop-ups will help to address the ongoing spike in cases and alleviate the long testing lines around the city.