Authorities tasked with marine monitoring announced there were no hazardous chemicals detected in waters off the blast site in north China's port city Tianjin on Friday.

A statement from the State Oceanic Administration (SOA) said major measurement of seawater composition did not show any anomaly compared with historical records.

Hazardous materials such as cyanide and volatile phenol were not detected, while the variety of zooplankton was not affected either, it added.

The results were made after 177 seawater samples were taken by local marine monitors in Tianjin. The SOA said it will update seawater status if major changes are found.

The warehouse blast, which occurred late Wednesday night, killed at least 50 people, including 17 firefighters. A total of 701 were injured, of whom 70 still in critical condition.

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