A toxic chemical has leaked into a river in Byelorussia and Latvia, forcing the shut-off of drinking water in the Latvian capital Riga and possibly affecting scores of villages, an official said today.

Drinking water from the Daugava River to Riga, a city of nearly 1 million, was turned off Thursday morning, said Viktor Yukhno, the controller at Latvia's water authority.The city's residents have been using water from underground wells, but pumps are not powerful enough to bring water to taller buildings and many residents remain without water, Yukhno said.

The chemical leaked Nov. 2 from a plant in the Byelorussian town of Novopolotsk, 480 miles from Riga, and 880 miles west of Moscow.

Riga Mayor Andris Inkulis said plant officials never informed area residents about the leak, and people first learned of the problem after fish began dying.

"This does not only affect Riga, but the whole (republic)," Inkulis said in Stockholm, Sweden, where he was visiting over the weekend. "We warned people over television and radio so they could save some water."

He said the town of Daugavpils, 120 miles east of Riga, had been affected more severely than the capital, but he gave no details.

The plant is believed to make chemicals for use in military weapons, Yukhno said.

The chemical was a component of cyanide, Yukhno said, but officials were still testing it to determine exactly what kind.