SAN JUAN, Puerto Rico - Ahh, the Caribbean. Sun, surf. But where's the sand?

It is disappearing at alarming rates as thieves feed a local construction boom.

Caribbean round grains, favored in creating smooth surfaces for plastering and finishing, are being hauled away by the truckload late at night. On some islands, towns and ecologically sensitive areas are now exposed to tidal surges and rough seas.

In Puerto Rico, thieves once mined the dunes in the northern town of Isabela, said Ernesto Diaz of the Department of Natural Resources. Now they are stealing the beaches of tiny Vieques, the 52-square-mile island where the U.S. military only recently halted its bombing practice.

Among the hardest hit is Grenada, where officials are building a $1.2 million seawall to protect the 131-square-mile island. Large-scale sand thefts have exposed north-coast towns to rough seas.

One of the region's largest thefts targeted Jamaica, where nearly 100 truckloads of sand were swiped from private property, exposing protected mangroves and a limestone forest to wind and waves.

Roughly 706,000 cubic feet of sand was taken in late summer, enough to fill about 10 Olympic-size pools, said Jamaica Mines Commissioner Clinton Thompson, who said he suspected government officials were involved. "This one could not have been stolen without persons knowing about it," he said.

Police have declined to comment on the investigation.

Front loaders

Illegal sand mining in the Caribbean began in the 1970s, when people with shovels stole small amounts for construction, because most homes were built with wood. But the thefts increased as builders switched to concrete homes and have gotten bigger with the rise in construction of resorts and hotels - built, ironically, for tourists drawn by the immaculate beaches.

Some islands offer local quarries or designate certain beaches for mining, but large-scale nighttime thefts persist despite patrols. Front loaders and other heavy equipment are now used instead of shovels to steal sand, which sells for nearly $200 a cubic yard.

No one knows how much sand in all has been carted away, but Tortola, Anguilla and St. Vincent are now vulnerable to flooding, said Gillian Cambers, a University of Puerto Rico researcher. Up to two-thirds of sand dunes in Tortola and Nevis have been decimated, she added.

Aquifer ruined

In Barbuda, illegal sand miners dug a 23-foot crater that damaged a freshwater aquifer. Saltwater seeped in, and droppings from cows and donkeys contaminated the exposed aquifer, which is now unusable, local environmentalist John Mussington said.

Hurricane damage also has bumped up demand for sand, with residents using concrete blocks to rebuild homes and sand to finish them. If caught, thieves face light fines and jail time that critics say are unequal to the crime.

Grenada imposes up to $190 in fines, less than the cost of a single load of sand. But legislators plan to triple that amount and extend prison terms from three months to two years. Jamaica plans to approve new maximum fines of $11,000.

Some islands considered importing sand to replenish the beaches, but officials say it is expensive, and they worry about shifting the problem elsewhere. Joseph Gilbert, Grenada's minister of Works and Environment, said action was needed immediately, "otherwise, we will lose our beaches."