The FBI on Thursday added the names of 10 Chinese to the list of those being sought for questioning about a possible terror plot targeting Boston.  

Two law enforcement officials, speaking on condition of anonymity because of the ongoing investigation, said the names were part of the same anonymous tip that led authorities on Wednesday to announce that they are seeking to question four other Chinese and two Iraqis.

The officials said the tip remains uncorroborated and there is no credible evidence that such a plot exists.

It was unclear why all the names were not announced at the same time. The officials said there was no new information that led to the addition of the 10 names.

A third federal law enforcement official in Washington, also speaking on condition of anonymity, said the tip was received Wednesday 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.

US Attorney 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."

"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."

White House Chief of Staff Andrew Card said he discussed the manhunt with US President Bush during an Oval Office meeting a few hours before Bush's inauguration for a second term. Card did not provide details on what was said.

The four Chinese previously named by the FBI were identified as Zengrong Lin, Wen Quin Zheng, Xiujin Chen and Guozhi Lin. Authorities said none of the names had appeared on previous watch lists of terror suspects. The bureau also released pictures of those four but not of the others being sought.

In Boston, there were visible signs of stepped-up security, including some underground parking garages searching vehicles as they entered and pictures of the Chinese suspects posted inside the booths where subway tokens are sold by transit employees.

It was from Boston's Logan International Airport that two of the planes involved in the September 11 terrorist attacks were launched, and tight security is something residents dealt with in the midst of the Democratic National Convention this past July.

Massachusetts Governor Mitt Romney, who skipped President Bush's inauguration to return to the state Wednesday night after learning of the threat, sought to reassure residents that there was nothing to be alarmed about.

"These kinds of threats are going to be received from time to time. Generally we're going to be able to deal with them in a prompt manner and dismiss them with time and evidence," Romney said. "It's our hope that this turns out to be an invalid hoax of some kind. ... And yet we take these things very seriously."

(Chinadaily.com.cn via agencies, January 21, 2005)