Thousands of Amazon workers have ended their days-long strike against the company, according to the Teamsters union. But tensions persist, with the union saying its efforts aren’t over.

Amazon delivery drivers and Starbucks baristas are on strike in a handful of U.S. cities as they seek to exert pressure on the two major companies to recognize them as unionized employees or to meet demands for an inaugural labor contract.

The International Brotherhood of Teamsters announced their support of an Amazon worker strike that started Thursday after the company didn’t meet the union’s deadline for bargaining negotiations with protesters.