The Bureau of Diplomatic Security said on Friday that a man suspected of carrying out the "despicable" arson attack on the Chinese consulate in San Francisco on New Year's Day had been arrested.
Local police have since enhanced the consulate's security presence.
However, the suspect's nationality and identification remained undisclosed due to the postponement until Monday of an FBI news conference originally planned for on Friday. The FBI did not explain the reason for the postponement.
Sources told China Daily a male Tibetan separatist seen standing in front of the consulate on Jan 1 holding a poster with some numbers on it was not connected with the arson attack.
"I am sorry that the New Year has started under such unfortunate circumstances for my consulate," Consul General Yuan Nansheng said at a Chinese New Year's reception for San Francisco-based media on Friday night. "But we are fortunate to have received numerous sympathy calls or notes from people from all walks of life. They share our anger over this cowardly and despicable act. I want to thank all of our friends for your warm words and strong support."
The consulate said video cameras recorded the arsonist at 9:25 pm on Wednesday night, carrying two buckets of gasoline from a van parked on Laguna Street, which he splashed onto the front door of the consulate before throwing something toward the glass window above the door to ignite the liquid.
Consulate spokesman Wang Chuan said there were no casualties and that the incident had done little to deter people from visiting the consulate for visa services in the following two working days.
A staff member, who refused to be named, told China Daily on Friday: "I had left my office quite near the front door only a few minutes before the arson attack. I heard the sound of a fire truck as I returned to my dormitory in the consulate complex.
"I didn't take it seriously at the beginning as I thought there are always some fire trucks passing by. I was shocked later when I saw the seriously damaged main entrance of the consulate."
The consulate has urged the United States to take all necessary measures to provide adequate protection for Chinese consular personnel and property.
Meanwhile, police in San Francisco have boosted security at the Chinese consulate general, the US State Department said on Friday.
"The San Francisco Police Department is providing 24/7 coverage at the Chinese consulate while the investigation continues," spokeswoman Marie Harf told reporters at a regular news briefing.
"We're looking into whether more security is appropriate," she added but refused to offer more details.
The FBI said on Thursday that it considered the incident a "criminal matter" and not an "issue of national security or terrorism".
Zhou Wa in Beijing contributed to this story.