Tropical Storm Jeanne killed two people and caused significant flooding in Puerto Rico on Wednesday as it swept over the island on its way to probably becoming the season's sixth hurricane.

A flying sheet of zinc roofing killed a woman who ran outside as winds tore up her roof, and a man trying to install storm shutters fell to his death, according to local media reports.

Floods and downed power lines were reported in the U.S. commonwealth of four million people, schools and airports were closed and many residents were leaving the coast for safer ground inland.

Gov. Sila Calderon ordered the electrical grid shut down to avert deaths, ordered public employees to stay away from their jobs until Jeanne passed and urged Puerto Ricans to stay indoors and remain calm.

Forecasters at the National Hurricane Center in West Miami-Dade County said Jeanne could become a hurricane today.

They said it was likely to brush the northeast coast of the Dominican Republic before rolling through the Bahamas and in the general direction of Florida. Long-range forecasts -- subject to large errors -- suggested that Jeanne could curve away from the state this weekend, but that remained uncertain.

Jeanne was reported to have made landfall in Puerto Rico near the southeastern town of Yabucoa just after noon. Storm warnings were posted for Puerto Rico, the U.S. and British Virgin Islands and parts of the Dominican Republic.

A Shell petrochemical refinery in Yabucoa was shut down as waist-high floods already covered some of the nearby roads by mid-Wednesday -- barely into the 24 hours of rain predicted from Jeanne.