LOS ANGELES (AP) — More than 50,000 Los Angeles County workers demanding higher pay were on strike again Tuesday, and the walkout caused closures or disruptions at libraries, healthcare clinics and administrative offices across the nation’s most populous county.

The two-day strike that began Monday evening followed failed negotiations with the county for a new contract after the last one expired in March, according to the Service Employees International Union Local 721.

The union represents employees including public health professionals, social workers, parks and recreation staff, custodians, clerical workers and others serving a county of 10 million residents. It’s the first time all of its about 55,000 members are on strike, the union said.

Marchers wore purple and hoisted signs reading “We are the safety net!” A huge crowd marched through downtown LA streets while pickets were planned at dozens of sites countywide, including Harbor-UCLA Medical Center and offices of the Department of Children and Family Services.

The work stoppage caused short staffing that led to long lines at the county’s Department of Public Social Services. Staff members on hand said they could print some paperwork and process documents but couldn’t give out case updates or handle other issues usually dealt with by social workers participating in the strike.

Michael Euring, 54, said he couldn’t pick up his mail or a new public assistance card. He didn’t know why the strike was happening but was frustrated by the disruption in services.

“I have a 7-month-old son, and I’m a single father,” Euring said. “The mail that I need is here. I can’t get an EBT card, can’t access my benefits to feed my child.”

Lauren Punch, a supervising clerk at the office who joined the walkout, called the situation “100% preventable.” She wants a salary increase as well fewer people to supervise.

“It’s disrespectful to the community that we’re charged to take care of,” Punch said. “It’s a shame that there are people out here with disabilities that we’re not able to service fully.”

The labor action is set to last until 7 p.m. Wednesday. Until then members of the public could experience closures or delays at libraries, some healthcare clinics, beach bathrooms and public service counters at the Hall of Administration. Services in the medical examiner’s office and public works department may also be affected, according to the county. But hospitals and most county offices will remain open.

“This is the workforce that got LA County through emergency after emergency: the January wildfires, public health emergencies, mental health emergencies, social service emergencies and more,” union leader David Green said in a statement. “That’s why we have had it with the labor law violations and demand respect for our workers.”

The union has accused the county of 44 labor law violations during contract negotiations, including surveillance and retaliation against workers engaging in union activity and contracting out work that’s supposed to be done by union members.

LA County says it’s facing “unprecedented stresses” on its budget, including a tentative $4 billion settlement of thousands of childhood sexual assault claims, a projected $2 billion in impacts related to the LA wildfires in January, and the potential loss of hundreds of millions in federal funding.

“We do not want to negotiate ourselves into a structural deficit — which could lead to layoffs and service reductions,” spokesperson Elizabeth Marcellino said in a statement from the chief executive office. “We are trying to strike a balance: fair compensation for our workforce while sustaining services and avoiding layoffs in the midst of some of the worst financial challenges we have ever experienced.”

The city of LA is facing similar financial woes — Mayor Karen Bass’s recently proposed budget includes 1,600 layoffs of city workers amid a nearly $1 billion deficit.

About 150 county workers picketed outside Los Angeles General Medical Center on Monday.

Lillian Cabral, who has worked at the hospital since 1978, said the strike was a “historic moment” that involved staff from the emergency room and radiology departments to custodians.

Cabral is part of the bargaining committee and said she was frustrated by a process that has been filled with long delays and little movement from the county.

“It’s so unfair to us, it’s so unfair to our patients, and to our clients and our community,” Cabral said.