SOFIA, Sep. 27 (Xinhua) -- A cargo ship sank Saturday morning in the Black Sea off the Bulgarian coast, with all crew members reported missing, local press cited the Bulgarian Transport Ministry as saying.

    It is still unknown how many crew were aboard the ship Tolstoy, which sank at about 4 a.m. local time (0100 GMT) some 12 miles off Cape Emine on Bulgaria's northern Black Sea coast, a spokeswoman for the ministry said.

    It is said that the ship was under the flag of the Democratic People's Republic of Korea.

    "The ship issued no SOS call and our authorities found out about the incident after 11 a.m. local time (0800 GMT) today after a signal was sent from another Black Sea country," she said, but giving no further details.

    Bulgarian air force helicopters are currently searching the area for survivors. Military and commercial ships are also participating in the rescue effort.

    However, rough weather is making it difficult rescuers to search any possible survivors.

    The area near Emine is most often used by ships traveling from Russia to Turkey.