Authorities in the northern Chinese province of Shanxi have apologized for waiting nearly a week to report a massive chemical spill into a major waterway, China Daily reported.

On Dec. 31, 2012, more than 9 tons of the toxic chemical aniline was released from a fertilizer plant in the nearby Zhuozhang River, killing fish and contaminating the water source for more than 1 million people.

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The incident, which was caused by a crack in a delivery pipeline to a storage tank, was not announced until Jan. 5. The mayor of Changzi city made a formal apology on Jan. 7 saying his government underestimated the severity of the incident.

Approximately 5,000 police officers, soldiers and workers are helping to clean up the contamination.

According to the U.S. Environmental Protection Agency, aniline is highly toxic to aquatic life.