SANTIAGO, Dominican Republic -- Tropical Storm Olga triggered floods and landslides on the Caribbean island of Hispaniola on Wednesday, killing at least 13 people and forcing thousands to flee their homes, authorities said. One person also died in Puerto Rico.

Hardest hit was the northern province of Santiago in the Dominican Republic, where heavy rains forced authorities to release water from a near-capacity dam into the already swollen Yaque river. The provincial governor said at least seven towns were completely flooded.

People complained on local radio that they were not warned of the water release from the dam, and officials acknowledged it might have caused some of the 10 deaths reported in the province.

"We have an emergency situation. It's a catastrophe," Gov. Jose Izquierdo said.

Olga weakened to a tropical depression Wednesday afternoon, but rain continued to fall from a system that forecasters said could bring as much as 10 inches to some parts of the Dominican Republic and Haiti, which share the island of Hispaniola.

At least 11 people were killed and 5,000 evacuated in the Dominican Republic, said Ismael Matias, planning chief of the Dominican emergency operations center.

An elderly woman and a 3-year-old boy were reported killed in northern Haiti, where poor infrastructure could delay reporting on the storm's aftermath for days, said Marie Alta Jean-Baptiste, head of Haiti's civil protection department.

The storm was also blamed for one death in Puerto Rico, where a rain-triggered avalanche buried an sport utility vehicle.

Families living along the banks of the swollen Yuna River near Santiago were evacuating, placing mattresses atop their heads and climbing aboard motorcycles headed toward higher ground. Trucks carrying soldiers headed toward Santiago province.

As heavy rains overwhelmed the Tavera Dam near Santiago, the country's second-largest city, officials decided to release water to prevent the dam from collapsing, said Octavio Rodriguez, a civil defense official on the committee that decided to flood the river.

By midnight Tuesday all of the dam's doors were open and 1.6 million gallons were pouring through every second.

"We knew the damage we were going to cause below. We did not want to, but we had to," Rodriguez told The Associated Press. In light of the potential catastrophe of a dam collapse, he called the resulting death toll "acceptable."

Local authorities had warned repeatedly that a release was possible during the storm and told people to evacuate areas in the path of river due to swells as high as 66 feet above the river's normal level, Rodriguez said. It was unclear if the warnings were heeded or even relayed.

Olga struck nearly two weeks after the official end of the Atlantic hurricane season. It is only the 10th named storm to develop in the month of December since record keeping began in 1851, according to the U.S. National Hurricane Center in Miami.

The storm passed through the southwestern areas of the Dominican Republic that were hardest hit by Tropical Storm Noel six weeks ago. At least 87 fatalities in the country were blamed on Noel, the deadliest storm of the 2007 Atlantic hurricane season.

The storm passed Puerto Rico on Tuesday night, knocking out electrical service to 79,000 people and water to 144,000.

Olga will be included in the tally for the 2007 hurricane season, bringing the number of named storms to 15, including six hurricanes. The next season begins June 1.

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Associated Press writers Jonathan M. Katz in Port-au-Prince, Haiti and Ramon Almanzar in Santo Domingo contributed to this story.