美国议员追究联邦各机构间的情报交流问题

U.S. lawmakers have raised concerns about the sharing of intelligence among federal enforcement agencies, as investigators continue to piece together last week's deadly bombing of the Boston Marathon.

Senator Lindsey Graham said Tuesday that the FBI told him it did not know last year that one of the bombing suspects, Tamerlan Tsarnaev, traveled to Chechnya and Dagestan.

Homeland Security chief Janet Napolitano told the Senate Intelligence Committee that her agency knew of the six-month trip, but that an FBI alert on Tsarnaev had expired by the time he returned.

The FBI had interviewed Tsarnaev in 2011 at the request of Russia, but found nothing to connect him to terrorism at that time.

After a closed-door briefing by FBI officials Tuesday, Republican Senator Susan Collins said there are problems with sharing of "critical investigative information" within and among different agencies.