WILLIAMSPORT, Pa. — Composite bats will no longer be used in the Little League World Series.

Little League officials announced a moratorium on the equipment Thursday based on research it commissioned from the University of Massachusetts in Lowell.

Composite bats have metal shells enclosing woven fibers inside the barrels.

Critics say the bats endanger youngsters because balls fly off them at high speeds and can injure fielders. Supporters say they are lighter and easier to handle.

Little League banned composite bats in its older junior, senior and big league divisions in August. The league broadened the ban on Thursday to include the younger majors division featured in the World Series.

Players can use wood bats, metal bats or bats with composite materials in the handle only.