WUHAN, Nov. 26 (Xinhua) -- Local authorities issued a navigation safety alert on Monday on account of the low water level in the Yangtze River caused by the worst autumn drought in 50 years.

    The "yellow warning", the second highest level, was sent out bythe Yangtze River Maritime Safety Administration for a 680-kilometer stretch of the waterway in the river's upper reaches.

    The announcement came after a cargo ship was grounded on the river on Wednesday evening, disrupting traffic for nearly 40 hours.

    The administration urged local authorities to send more staff to check for overloading, inspect ship gauges and quickly update information on water levels and weather forecasts.

    It also asked ship operators to navigate cautiously, and use GPS and radar to minimize the possibility of accidents.

    Prolonged drought has caused a severe build-up in silt along the river, with water levels in some sections falling one meter lower than last year.

    Local river bureau authorities began dredging the river much earlier this year and used more equipment to clear the silt.