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.