MATAMOROS: Alex, the first hurricane of the Atlantic season, weakened across northeast Mexico Thursday, leaving at least one person dead after disrupting oil clean-up operations in the Gulf of Mexico.

Heavy rainfall remained a major hazard over northeast Mexico and southern Texas, where the Miami-based National Hurricane Center (NHC) also predicted more possible isolated tornadoes.

Television pictures showed rivers gushing beyond their banks, uprooted trees, fallen traffic lights and floating cars.

One person drowned in Mexico`s northern city of Monterrey, Luis Carlos Trevino, the Nuevo Leon state governor, told journalists.

Two workers were also crushed to death by a falling wall and another person was missing, but Trevino said the incidents may not have been linked to Alex.

At least 11 people were killed over the weekend when the storm passed through Mexico`s Yucatan peninsula, Nicaragua, Guatemala and El Salvador.

Alex was downgraded to a tropical storm after roaring ashore again late Wednesday as a Category Two hurricane slightly south of the eastern US-Mexico border, in Tamaulipas state.

Almost all 250,000 inhabitants of the state capital Ciudad Victoria suffered water and power cuts and communications were widely interrupted, Salvador Trevino, a local civil protection official, told AFP.

The coastal state saw widespread flooding, schools were closed, and thousands of people remained in temporary shelters on Thursday.

Mexico`s Meteorological Service warned that the storm would produce "intense and torrential rain, strong winds and an elevated surge" through Friday across five Mexican states.

"These rains could cause life-threatening flash flood and mud slides," the NHC warned.

At 2100 GMT, Alex was moving westwards and losing steam, according to the NHC.

Maximum sustained winds decreased to near 40 miles per hour (65 km per hour) and Alex was expected to dissipate over high ground overnight.

Alex disrupted clean-up operations for the massive BP oil spill in its passage through the Gulf of Mexico.

Although the storm traveled far southwest of the worst hit area -- the coasts of Louisiana, Mississippi, Alabama and Florida -- its strong winds whipped up choppy waves, forcing a halt in skimming operations.

Large waves also pushed more of the huge slick onto fragile shorelines.

US officials said the storm interrupted 26.3 percent of crude oil production in the Gulf on Wednesday.

Alex is the first Atlantic hurricane to form in June since 1995, according to the National Hurricane Center.

BDST: 09:51 HRS, July 2, 2010