UPDATE 1-Ternium kicks back after Mexico watchdog halts wastewater release

Updates with details from Profepa, Ternium, background

MEXICO CITY, Jan 15 (Reuters) - Steelmaker Ternium TX.N said on Wednesday said that wastewater from a plant in Mexico was not a pollutant, after the country's environmental watchdog Profepa said it had ordered Ternium to temporarily halt the flow of wastewater out of the site.

Profepa said Ternium had been spilling its wastewater in a tributary of the Atoyac river without a permit, but Ternium said this was not the case and that the problem with the regulator was over ongoing bureaucratic processes concerning "inconsistencies" in the name of the company on permits.

The Atoyac river in central Mexico is one of the most-polluted rivers in the country, and President Claudia Sheinbaum has said that cleaning up the waterway, which receives wastewater from nearby factories, will be a priority during her administration.

"We are waiting for a favorable resolution from (water authority) CONAGUA to conclude the process," Ternium said in a statement, noting that apart from the halt on wastewater flows, its plant was operating normally.

Profepa said on Tuesday that the order was part of a multi-agency strategy to clean up the Atoyac, alongside other heavily polluted rivers.

Ternium is one of Latin America's largest steelmakers, with 18 factories across the region, many in Mexico where it supplies automakers exporting cars to the United States.

In the first nine months of last year, it shipped 6.2 million tons of steel in Mexico, earning some $6.7 billion in net sales in the country alone.

(Reporting by Raul Cortes and Sarah Morland; Editing by Kylie Madry)

((sarah.morland@thomsonreuters.com;))