Washington ? The FBI on Thursday added the names of nine Chinese people and one other man to the list of those being sought for questioning about a possible terror plot targeting Boston.

FBI spokesman Joe Parris said the names “were developed as a result of the ongoing investigation” but did not signal that credible evidence has emerged indicating such a plot actually exists.

“Information is still uncorroborated and from a source of unknown reliability and motive,” Parris said.

The names are part of the same anonymous tip that led authorities to announce Wednesday they were seeking to question four other Chinese and two Iraqis. The new names bring to 16 the people being sought for questioning.

Another federal law enforcement official in Washington, speaking condition of anonymity because of the ongoing investigation, said the tip was received by the California Highway Patrol. The tipster claimed the four Chinese — two men and two women — entered the United States from Mexico and were awaiting a shipment of “nuclear oxide” that would follow them to Boston.

The official said the nuclear oxide could be a reference to material used to make a “dirty bomb” that would spew radiation over a wide area.

U.S. Atty. Michael Sullivan of Boston said earlier Thursday that authorities had learned more background about the original four Chinese, but “it makes us no more alarmed this morning, this afternoon, than we were yesterday.”

Massachusetts Gov. Mitt Romney, at microphone, skipped President Bush's inauguration to return to the state after learning of a terror threat. Romney and other officials urged Boston residents to carry on as usual Thursday while authorities sought possible suspects in an alleged bomb plot.

“They’re not wanted at this point in time for any crimes because there’s no evidence at this point in time that they’ve committed any crimes,” Sullivan said. “We’re not certain exactly where they are. We can’t even say for certain that they’re in the country.”

The four Chinese previously named by the FBI were identified as Zengrong Lin, Wen Quin Zheng, Xiujin Chen and Guozhi Lin.

One woman was among the nine new Chinese names added: Yu Xian Weng, a woman either 40 or 41 years old. The others were all men: Quinquan or Quiquan Lin, 21; Liqiang Liang, 28; Min Xiu Xie, 27; Xiang or Xing Wei Liu, 22; Mei Xia Dong, 21; Xiuming Chen; Cheng Yin Liu; and Zao Yun Wang.