BOSTON – The FBI notified law enforcement officials yesterday to be on the lookout for four Chinese nationals described as possible terror suspects who may be headed to the Boston area.

Federal law enforcement officials said they had received a tip about an unspecified threat against Boston, and released photographs of the two men and two women they were seeking. Authorities said none of the names had been on previous watch lists of terror suspects.

The investigation stirred a frenzy of press reports and prompted Governor Romney, who had gone to Washington to attend today’s presidential inauguration, to decide to return to Massachusetts later yesterday.

Mr. Romney cautioned that the threats were unsubstantiated and uncorroborated. “We have had threats in the past. We take them seriously, even when they’re not corroborated,” he said.

Mr. Romney said the state’s threat level would not be raised, but more people would be on duty in the state’s emergency management bunker.

“To assure the people of Boston and Massachusetts that it is safe to be at home, I am going to be sleeping in my bed in Massachusetts tonight and I feel perfectly safe doing so,” Mr. Romney said. “In the very remote circumstance that my attention is needed, I will be able to respond on an immediate basis.”

A federal law enforcement official, speaking on condition of anonymity because the matter remains under investigation, told the Associated Press that the FBI’s joint terrorism task force has not yet corroborated a tip that the suspects entered America through Mexico in recent days, possibly bound for Boston.

The official stressed the tip is one of many from around the country that routinely are forwarded to local task forces for further investigation.

In a joint statement issued by Massachusetts U.S. Attorney Michael Sullivan and Kenneth Kaiser, an agent in charge of the Boston FBI office, the suspects were identified as: Zengrong Lin, Wen Quin Zheng, Xiujin Chen, and Guozhi Lin.