(CNN) -- Venezuela continues to nationalize private businesses, with President Hugo Chavez announcing late Monday that the government will take over two U.S.-owned Owens-Illinois glass-manufacturing plants.
Chavez also ordered an environmental investigation at the sites, the state-run Agencia Venezolana de Noticias reported.
Owens-Illinois did not know what will happen next, a spokeswoman said Tuesday.
"We haven't received official word from the government yet," said spokeswoman Stephanie Johnston.
Venezuelan military personnel were at the company's plant in Los Guayos, Johnston told CNN. No Venezuelan authorities were on the scene at the company's plant in Valera, Johnston said.
"Both plants continue to operate as usual," she said.
Owens-Illinois Inc. says it is the world's leading glass container maker with more than 22,000 employees in 21 countries. The $7.1 billion company has global headquarters in Perrysburg, Ohio.
Chavez, who has nationalized other industries and land holdings during his 11-year tenure, said he soon will announce the takeover of other foreign companies that have been "exploiting the country's working class."
U.S. officials said Tuesday they were monitoring developments.
"We've seen the announcement and are following the situation closely," the State Department said. "We would expect Venezuela to provide prompt, adequate and effective compensation for any expropriation of the investments of Owens-Illinois in accordance with international law."
Chavez nationalized a local unit of U.S. food giant Cargill last year. He previously has appropriated privately owned oil, telecommunications, power, cement and steel companies.
CNN's Arthur Brice and Juan Carlos Lopez contributed to this report.