U.S. oil major Chevron Corp. has evacuated executives from Venezuela after two of its workers were imprisoned over a contract dispute with state-owned oil company PDVSA, according to four sources familiar with the matter.

Chevron asked other employees to avoid the facilities of its joint venture with the OPEC nation's oil firm, the sources said.

The arrests, in a raid by national intelligence officers, were the first at a foreign oil firm since Venezuela's government launched a purge last fall that has resulted in detentions of more than 80 executives at PDVSA and business partners.