"So far, we've been unable to get the answers we need to know what happened to Shane Todd," Baucus said.
Baucus has repeatedly noted that there was no clear evidence the young engineer was a victim of a homicide, but the strangeness of the elements of the incident "adds up."
"It seems fishy," he said. "I have deep concerns about potential foul play and potential breaches of national security but I don't have the facts yet."
When asked by reporters, Baucus said the diplomatic relations between the country had not changed, but indicated the government would respond if it found evidence Singapore had been "stonewalling" investigations.
Mary and Rick Todd say this case isn't just about their son's death but also a matter of national security.
"Mary and I are both committed to seeing this to the end and that our country is protected," Rick Todd said. "We need to wake up."
ABC News' Matthew Larotonda contributed to this report.