"The embassies and consulates that we closed over the weekend will remain closed until Saturday, as we initially said," department deputy spokeswoman Marie Harf told British newspaper The Guardian in Washington before Yemen's official SABA news agency backed away from at least part of the government's earlier assertions.
"No plans for that to change at this time," she said.
"A threat remains," department spokeswoman Jen Psaki told reporters.
Yemeni government spokesmen had said the country's security forces had uncovered and foiled several al-Qaida plots -- including planned attacks against a major Yemeni oil and gas facility, military installations and Western embassies.
"We of course have seen those reports," Psaki said after the claim and before the news agency distanced the government from it.
"I'm not going to get into any specifics," Psaki said.
"Our embassy remains closed. We're continuing to evaluate all information on a daily basis. But beyond that, I don't have an additional update."
The Wall Street Journal said U.S. officials cast doubt on the claims' authenticity.
SABA later cited security sources who denied there had been a threat against the oil and gas facility.
Another Yemeni official told CNN the alleged plot the government spokesman referred to was apparently unrelated to the terrorist threat that Washington blamed for the closing of U.S. embassies. The alleged threat also prompted a U.S. warning for Americans to leave Yemen.
Yemen's capital, Sanaa, remained on high alert Thursday, with jet fighters overhead and streets barricaded.
Three drone strikes early Thursday east of Sanaa killed at least three people, witnesses cited by The New York Times said.
The strikes hit one of two cars carrying alleged al-Qaida members, the witnesses said.
One car allegedly carried a leading al-Qaida member from Saudi Arabia, but the witnesses said they didn't know if he was in the vehicle that was struck.