MEXICO CITY (Reuters) - Tropical Storm Helene made landfall off the Gulf of Mexico on Saturday and weakened into a tropical depression as it plowed up Mexico's east coast, the U.S. National Hurricane Center said.

The depression was about 65 miles west-northwest of Tampico and had maximum sustained winds of 30 miles per hour, the NHC said in its 4 p.m. CDT (5.00 p.m. EDT) bulletin.

Tropical storm warnings were discontinued on the Mexican coast, although Helene still was expected to produce two to four inches of rain in the states of Veracruz and Tamaulipas.

Helene was predicted to continue weakening and dissipate within 48 hours, the NHC said.

There were no reports that Helene had affected the Gulf of Mexico's oil installations, which are built to resist powerful hurricanes.

Last week, Hurricane Ernesto hit Mexico, unleashing rains and winds that caused six deaths.

(Reporting By Ioan Grillo; Editing by Paul Simao)