Officials have updated the death toll to 138 from a powerful tornado that hit the central U.S. city of Joplin, Missouri last month.

Missouri public safety officials said Thursday the toll rose after four hospitalized people died from injuries suffered during the tornado.

The twister tore through Joplin on May 22 with winds topping 300 kilometers an hour, tearing apart homes and buildings, crushing cars and snapping trees.

The U.S. National Weather Service says the tornado was the deadliest to hit the U.S. since 1947.

On Wednesday, four people were killed when the latest in a string of tornadoes to hit the U.S. in recent weeks struck the western area of Massachusetts, a region where tornadoes are relatively rare.

Tornadoes have killed more than 500 people in the United States this year, the highest annual toll since 1950.