WASHINGTON — A senior Republican senator said Friday that the approaching political debate about an immigration overhaul should take into account the revelation that the suspects in the Boston Marathon bombing had apparently emigrated to the United States from Kyrgyzstan.

Senator Charles E. Grassley of Iowa, the most senior Republican on the Senate Judiciary Committee, opened a hearing on immigration legislation by stressing the issue’s importance “particularly in light of all that’s happening in Massachusetts right now and over the last week.”

“Given the events of this week, it’s important for us to understand the gaps and loopholes in our immigration system,” Mr. Grassley said in his opening statement. “While we don’t yet know the immigration status of people who have terrorized the communities in Massachusetts, when we find out, it will help shed light on the weaknesses of our system.”

Friday’s hearing was expected to offer an early glimpse into how the Senate would react to immigration legislation that a bipartisan group of senators introduced this week. Instead, it was overshadowed by developments in the Boston bombing case, which also affected the meeting directly when the homeland security secretary, Janet Napolitano, who was scheduled to testify before the committee on border security and enforcement, had to cancel her appearance to oversee her department’s involvement in the investigation.