* Local residents oppose shale gas
* Romania has substantial reserves of recoverable gas-US data
BUCHAREST Dec 2 U.S. oil major Chevron has resumed its search for shale gas in eastern Romania, it said on Monday, despite opposition from local residents.
In October the company won approval to drill exploratory wells in the small town of Pungesti in the impoverished eastern county of Vaslui but had to halt works soon after as local residents blocked access to the site.
Thousands of people have rallied across Romania in recent months to protest against government support for shale gas exploration and separate plans to set up Europe's largest open cast gold mine in a small Carpathian town.
"Chevron can confirm that it has resumed operations," the company said in a statement.
"Our priority is to conduct these activities in a safe and environmentally responsible manner consistent with the permits under which we operate."
On Monday up to 300 riot police were in Pungesti, 340 km (210 miles) northeast of capital Bucharest, blocking a road and barring residents from the Chevron site, a spokeswoman told local television stations.
Villagers have been taking turns guarding the site since October, sleeping in tents. They oppose the project and say they do not want what they say are the environmental risks of hydraulic fracturing, or fracking - the process of injecting water and chemicals at high pressure into shale formations to release the gas.
The U.S. Energy Information Administration estimates that Romania could potentially recover 51 trillion cubic feet of shale gas, which would cover domestic demand for more than a century.
Chevron, which also has rights to explore three licence blocks near the Black Sea, does not have plans to use fracking under its five-year exploration programme.