New Mexico nuclear waste dump, which saw a radiation leak in February, has halted shipments of toxic waste barrels to a commercial Texas facility amid concerns that chemical reactions could trigger another release there, officials said on Friday.

A probe found the February 14 accident may have been linked to improperly prepared and packaged drums of toxic waste accepted from the Los Alamos National Laboratory by the Waste Isolation Pilot Plant (WIPP), its managers said in a statement.

Investigators are still evaluating whether a chemical reaction caused the leak of unsafe concentrations of radiation in the underground salt caverns where waste is stored, which exposed 21 workers above ground to low levels of contamination.

"As they evaluate this possibility, it is prudent to temporarily stop shipments of this specific (Los Alamos lab) waste stream" to a commercial storage facility in Texas, managers said.

The WIPP complex in the Chihuahuan Desert in southeastern New Mexico was designed to permanently seal in salt chambers clothing, tools and other materials contaminated with radioisotopes like plutonium from U.S. nuclear labs and weapons sites.

There may have been chemical reactions between nitrate salts in radiological materials and organic materials such as plastic packing in barrels of waste from the Los Alamos lab, Jim Blankenhorn, deputy manager with the contractor running WIPP, told a public meeting on Thursday.

Fifty-five of the suspect barrels were stored in the salt chamber where the accident happened and additional drums from the same waste stream are in a separate disposal area below ground, Blankenhorn said.

Los Alamos chemists are seeking to develop a process for filtering out the nitrate salts before packing and shipping containers of waste, he said.

The repository is not expected to resume operations for at least 18 months but it may take as long as three years to be fully operational, Blankenhorn said.

(Reporting by Laura Zuckerman in Salmon, Idaho; Editing by Eric M. Johnson and Clarence Fernandez)