Canadian diversified miner Teck Resources Ltd is investigating another spill at its Trail smelting complex in British Columbia, but said on Sunday it does not expect the incident to have a long-term impact on fish or the environment.

Up to 25 cubic meters (883 cubic feet) of a solution containing some sodium hydroxide was released into a sewer line on Tuesday, Teck said in a statement. The sewer leads to a treatment plant that discharges into the Columbia River.

Sodium hydroxide is a corrosive chemical that when concentrated can burn and blister skin. The liquid released at the Trail facility, home to one of the world’s largest zinc and lead smelting and refining complexes, was diluted with water.

“Initial information indicates that the sewage treatment plant process may have diluted the high pH solution somewhat but otherwise had a limited effect,” Teck spokesman Richard Deane said in an email on Sunday.

Deane said Teck is investigating the incident, and outside experts will complete an environmental impact assessment.

In May 2011, Teck agreed to pay a C$325,000 penalty for two chemical spills at Trail, including one that saw mercury released into the Columbia River, which flows south into Washington state.

A U.S. law firm filed a class action lawsuit against Teck in December, alleging that pollution from Trail has caused health problems in the Northport, Washington area. Lead plaintiff Barbara Anderson has been diagnosed with breast cancer and inflammatory bowel disease, the suit said.

Teck is still reviewing the complaint, but said a 2004 U.S. government study found no link between rates of inflammatory bowel disease in Northport and the company’s Trail operations. The miner said it has spent more than $1.5 billion to modernize Trail, cutting the amount of metal released into the air and water by 95 percent since the mid-1990s.