Crude oil that spilled from a ruptured pipeline has blackened a river in eastern Venezuela, and the state oil company said workers are containing the spill.

Workers have removed a "good percentage of the crude" from the Guarapiche River in Monagas state, said Ramiro Ramirez, environmental director of state oil company Petroleos de Venezuela SA.

Mr Ramirez told the state-run Venezuelan News Agency that workers have been using absorbent barriers to block the crude in the river.

He said they have also shut off water intakes along the river, where a drinking water purification plant is located.

State oil company officials said a pipe that transports crude to a processing plant ruptured on February 4. Mr Ramirez did not say how much crude has spilled. He said officials were investigating what caused the accident.

Governor Jose Gregorio Briceno said earlier in the week that the government had declared an emergency in Monagas state after the spill forced officials to halt normal water distribution to parts of the city of Maturin, the Venezuela television station Globovision reported.

Mr Briceno said classes have been cancelled at schools in affected areas, and public offices have reduced hours due to the water supply problems.