'Poison' Obama letter seized as China mourns death of student in Boston
Envelope suspected of containing deadly ricin intercepted by authorities as China mourns student killed at Boston Marathon

A letter addressed to US President Barack Obama suspected of containing the deadly poison ricin was intercepted at a mail-screening facility outside the White House yesterday, as China mourned the death of a mainland graduate student in the Boston Marathon bombing.
The interception of the Obama letter came a day after another screening site intercepted a ricin-tainted letter bound for the office of Senator Roger Wicker.
While the FBI said investigations had not found a link between the letters and the Boston attack, their discovery increased tension two days after twin bombs killed three people and injured more than 170.
Among the dead was a mainland student studying at Boston University, who was described by shocked friends as a girl dedicated to her work.
The Chinese consulate in New York and Boston University confirmed a graduate student had been killed, but did not disclose personal details. However, mainland internet users identified her as Dorothy Lu Lingzi , who went to Boston University last year for a master's programme in mathematics and statistics.
President Xi Jinping offered condolences to the victims and ordered Chinese diplomatic missions in the US to offer assistance, Xinhua reported.
Lu's last microblog entry was posted on Monday with a picture of a bowl of Chinese fried bread and a tweet that said: "My wonderful breakfast." More than 200,000 condolence messages were posted on the entry.