Los Angeles, April 20 (IANS) Thousands of fish have been found dead at the Ventura harbour near Los Angeles, alarming officials about possible environmental hazards.

Officials Tuesday launched an investigation into the mystery behind the second mass death of fish near Los Angeles in more than a month.

Thousands of anchovies and sardines were found dead Monday, Xinhua reported.

A preliminary investigation found that the fish died due to lack of oxygen in the water after moving into the harbour a week ago, the Ventura Harbor Patrol said.

It, however, remained unknown as to why the fish entered the harbour. They could have been chased by a sea lion, dolphin or strong tide, officials said.

Pat Hummer of the harbour patrol said patrol boats drove around scooping up dead fish before they started sinking and stinking. They filled up over 20 barrels weighing 50 gallons.

In March, 175 tonnes of sardines died at the Redondo beach in King Harbor near Los Angeles.

Scientists said poisoning from acid generated by an offshore algae bloom might have been a possible cause for the deaths.