The content of the letter is classified, according to a Snowe spokesman and their office is not permitted to reveal the names of the colleagues who signed it.
While some Republicans have called for a special investigation into the issue, Feinstein dismissed it as impractical at this time.
"A special prosecutor can take years. We don't have years," she said. "Wherever the chips fall, they fall. We want a fair investigation. We want to see that we have the process in place to deal with this. I do not believe that we do at the present time."
Obama himself responded to the charges made by some lawmakers that his White House had authorized the leaks for political gain.
“The notion that my White House would purposely release classified national security information is offensive,” he told reporters during an economic briefing on Friday. “It’s wrong and people I think need to have a better sense of how I approach this office and how the people around me here approach this office.”
He said such leaks put people at risk, and his administration doesn’t “play around with that.”
“Since I’ve been in office my attitude has been zero tolerance for these kinds of leaks and speculation,” he said. “Now we have mechanisms in place where if we can root out folks who have leaked they will suffer consequences. In some cases, these are criminal acts when they release information like this and we will conduct thorough investigations as we have in the past.”
Ultimately, there may not be much anyone can do to stop such leaks, says Patrice McDermott, president of OpenTheGovernment.org, a group that promotes government transparency.
"In terms of what [Congress] can do to actually prevent leaks, it's probably pretty limited," she says. "It's already a civil offense, they can lose their security clearances, there are only certain kinds of information that are criminal offenses."
She says the Obama administration, under pressure from Congress, has already been pressured to prosecute leakers.
"A lot of the prosecutions that the Obama administration has undertaken for at leaks of classified information have been at least in part a result of pressure from members of Congress to get tougher," she says. "There's just not a lot that [Congress] can do because the authority already is there for the executive branch to prosecute this and the problem has always existed."
McDermott says there has always been a tension between the public's right to know what their government is up to and protecting people on the front lines.
"We do need information in order to hold government accountable and to have public debates on particularly things like the kill list and the use of drones to target individuals including American citizens and it's impossible to have an informed debate without information," she says. "There really are secrets that need to be protected … but we do have to have a way to debate these issues that are of major public concern. This has been going on forever. It's nothing unique to this administration."
Rebekah Metzler is a political writer for U.S. News & World Report. You can contact her at email@example.com or follow her on Twitter.