Trash continued to pile up across more than a dozen Eastern Massachusetts towns and cities as garbagemen remained on strike for a fifth day, this time with support from a local firefighter’s union. A contingent of the 450 members of Teamsters Local 25 continued their strike as negotiations continue with Republic Services, a waste management company with operations across the nation including Massachusetts, with a demonstration Saturday afternoon on Newbury Street in Peabody. But they weren’t alone: members of Peabody Firefighters Local 925 union showed up in solidarity. “We will be delivering supplies and walking the line with our fellow union brothers and sisters in their ongoing fight for fair wages, safe working conditions, and dignity on the job,” Peabody Firefighters union president Kory Desmond wrote in a call to action for “solidarity.” The strike in Massachusetts began on the first of the month, according to the Teamsters union, which added that other Teamsters unions are having similar contract disputes with Republic. “The strike will take as long as necessary to make certain that Republic Teamsters get what they’ve rightfully earned,” Thomas G. Mari, the president of the local Teamsters union, said in a recent statement. Republic has countered that the union is engaging in criminal practices as negations continue, including “slashing tires on occupied vehicles, harassing drivers out servicing customers, threatening employees and sabotaging trucks,” according to earlier Herald reporting.