The world's biggest iceberg, believed to be about the size of Hong Kong, is slowly melting in Antarctica and appears to pose no threat to shipping, a news agency reported Wednesday.

The iceberg, which has been code named B9, is the longest ever accurately recorded and has traveled a 620-mile circle since it broke away from the Ross Ice Shelf 18 months ago, the New Zealand Press Association said.The agency said scientists had been worried it might block the entrance to the U.S. research base at McMurdo Sound, where 700 people live during the Southern Hemisphere summer.

When it first cracked off the shelf, it was 95 miles long, 22 miles wide and 1,155 feet thick.