The National Security Agency intercepted private e-mail messages and phone calls of Americans in recent months on a scale that went beyond the broad legal limits established by Congress last year, government officials said in recent interviews. Several intelligence officials, as well as lawyers briefed about the matter, said the N.S.A. had been engaged in overcollection" of domestic communications of Americans. They described the practice as significant and systemic. The legal and operational problems surrounding the N.S.A.'s surveillance activities have come under scrutiny from the Obama administration, Congressional intelligence committees and a secret national security court. Congressional investigators say they hope to determine if any violations of Americans' privacy occurred. It is not clear to what extent the agency may have actively listened in on conversations or read e-mail messages of Americans without proper court authority, rather than simply obtained access to them. While the N.S.A.'s operations in recent months have come under examination, new details are also emerging about earlier domestic-surveillance activities, including the agency's attempt to wiretap a member of Congress, without court approval, on an overseas trip. After a contentious three-year debate that was set off by the disclosure in 2005 of the program of wiretapping without warrants that President George W. Bush approved after the Sept. 11 attacks, Congress gave the N.S.A. broad new authority to collect, without court-approved warrants, vast streams of international phone and e-mail traffic as it passed through American telecommunications gateways.