Singapore asked Indonesia on Monday for an update on the fate of granite shipments bound for Singapore's booming construction industry that the Indonesian navy detained last month, according to the AP. The detention of the tugboats and barges in late February came soon after Indonesia banned exports of sand used to make concrete for resource-poor Singapore on Jan. 23. Indonesia cited environmental concerns and fears that sand exports could shrink Indonesia's borders. But there has been no ban on exports of granite, and the detention of the vessels has become another irritant amid the sometimes testy relations between the two neighbors.