Troops found more than 839 tons of drug precursor chemicals at a warehouse in the central city of Queretaro, the largest such seizure in Mexican history, the Defense Secretariat said.

The chemicals, used to make synthetic drugs such as crystal meth, were discovered Monday at a warehouse in the city's industrial zone, the secretariat said in a statement.

No arrests were reported in connection with the seizure.

This week's confiscation tops the previous record of 200 tons of precursors seized almost a year ago in the Pacific port of Manzanillo.

Mexico, which produces most of the crystal meth consumed in the United States, has imposed tight restrictions on the import of chemicals used to make illegal synthetic drugs.