U.S. and Chinese oil companies are facing harsh criticism for their failure to disclose an oil spill off the eastern coast of China for almost a month.

The environmental group Greenpeace said it is “disappointed” in the delays in reporting the spill, which has contaminated 840 square kilometers in Bohai Bay off the coast of eastern Shandong province. China’s Communist Party-controlled Global Times quoted fishermen and energy experts Wednesday saying a government regulatory agency had failed to live up to its responsibilities.

The State Oceanic Administration held its first press conference on the spills Tuesday in Beijing after word began to spread through local newspapers and Internet blogs. The agency said oil seepage was first reported to the agency on June 4 and a second incident was reported on June 17.

The oil field is managed in part by the China National Offshore Oil Corporation, China’s largest offshore oil and gas producer. But CNOOC was quoted in Chinese media Tuesday blaming the leaks on its U.S. operating partner, ConocoPhillips.

The American company defended its role in the operations at a press conference in Beijing Wednesday. The Associated Press quoted the company saying it responded promptly to contain the damage from the leaks.

The State Oceanic Administration said Tuesday that it reported the situation to the State Council, China’s cabinet, and to local governments so they could notify fishermen in the area.

But Chinese media quoted fishermen saying they had not been told of the oil spills and complaining of dead seaweed and rotting fish in the bay.

Global Times said the State Oceanic Administration attributed delays in disclosing the spills to “technical restrictions” in collected data to map out the situation. It quoted U.S. climate and energy expert Yang Fuqiang saying the government should have publicized the spills much earlier.