The protest, which began around 9 a.m. at Levi's Plaza at 1155 Battery St., will continue "until Levi's gets our message," Greenpeace spokeswoman Myriam Fallon said.
Protesters have created a "foam river" in the plaza, and say they have models in Levi's jeans wading in the "river." Demonstrators said the foam river represents the rivers in Mexico that are being polluted by factories used by Levi's.
Fallon said some waterways in Mexico are being covered in unnatural foam created by chemicals used in dyeing, weathering and other parts of the manufacturing process for Levi's denim products.
"We're showing them what their pollution looks like," Fallon said.
Fallon said Greenpeace researchers have found that chemicals in the factories' wastewater are hormone-disrupting and harm aquatic life.
The company has responded to Greenpeace's campaign, which has been under way since 2011, agreeing to take steps in greening its supply chain.
In a statement on the company's blog that was posted Dec. 6, the company said, "... we agree with Greenpeace that the industry needs to take this seriously and think differently about how we use chemicals. Levi Strauss & Co. will continue to be a leader in this effort."
According to the company, it has committed to stop producing products with perflourinated compounds by July 2016, and has already stopped using alkyl phenol ethoxylates.
"Given the vast breadth and depth of global supply chains, the fact that many factories from many different industries often release wastewater into the same bodies of water, and the fact that our industry has long-established practices, change isn't going to be easy -- it will require investment, innovation, collaboration, and perseverance," the company's statement read.
The company also outlined its efforts with Joint Roadmap, an industry-wide plan that includes partners at Adidas, H&M, Nike and Puma, to cut down on the use of hazardous chemicals by 2020.
Greenpeace and Levi's representatives said Wednesday's protest is peaceful.