The U.S. Environmental Protection Agency on Friday ordered General Electric Co to dredge deeper into the Hudson River as part of the next phase of an effort to remove cancer-causing chemicals dumped into the river over decades.

GE, the largest U.S. conglomerate, also must remove more contaminated sediment instead of capping and sealing the river bottom to get rid of polychlorinated biphenyls, or PCBs. The company has until Jan. 14 to review the decision and notify the agency about how they plan to best proceed with the next phase of the cleanup, which is due to begin in May.

"We've said from the start that a clean Hudson is non-negotiable, and the path we have laid out today relies on the best science to ensure this dangerous pollution is addressed in an effective way," regional EPA administrator Judith Enck told reporters.

The EPA found that GE plants at Fort Edward and Hudson Falls, both in New York, discharged about 1.3 million pounds (590,000 kg) of PCBs during a 30-year period ending in 1977, when GE stopped using them as an insulator in electric components.

PCBs are human carcinogens and can also affect the immune, reproductive, nervous, and endocrine systems. One of the project's main goals is to achieve significant reduction in PCB levels in fish tissue.

The project addresses a 40-mile (64-km) stretch of the upper Hudson River from Hudson Falls to Troy, about 150 miles (240 km) north of New York City.

GE Chief Executive Jeff Immelt declined to comment on the cost of the work in comments to reporters this week but said the company was close to a deal on financing the river's future cleanup.

"We're going to really take the dredging of the Hudson off the table for future years," Immelt told reporters on Tuesday. "It's to complete the project."