Dumoulin, riding for Cofidis, finished the 206-kilometer (128-mile) ride from El Vendrell to Tarragona in 4 hours, 49 minutes, 31 seconds.

“It is a confirmation of my work, I am very happy to continue winning,” the 30-year-old Dumoulin said.

Contador, of SaxoBank, finished out of the top 10, but kept the leader's jersey. He remained 23 seconds ahead of American rider Levi Leipheimer and Italy's Michele Scarponi.

“In this race it takes a lot to remain leader. Not only for the mountain (stage), but also for days like today, with 210 kilometers, you need a very strong team to control breaks,” Contador said.

On Thursday, the International Cycling Union decided to challenge Contador's acquittal by the Spanish cycling federation for a positive test for clenbuterol while winning his third Tour de France last year.

The Court of Arbitration for Sport said it's aiming to give a verdict before the Tour de France starts July 2.

Since being cleared by the Spanish federation of a proposed one-year ban in late January, Contador has competed twice, finishing fourth in the Tour of Algarve in Portugal and winning the Vuelta of Murcia in Spain.

The Volta of Catalunya, which is celebrating its 100th anniversary, finishes Sunday.