As the U.S. Senate heard testimony Wednesday on legislation to toughen proof-of-identity requirements for driver's licenses, immigration lawyers and officials of the Pennsylvania Department of Transportation met in Philadelphia to scrutinize the process of deciding who gets a license here.

"Driver's licenses can be the keys to the kingdom for terrorists bent on death and destruction," Sen. Susan Collins (R., Maine) told the Homeland Security and Governmental Affairs Committee. "States have a responsibility to ensure licenses are tamper-proof and issued only to people whose identity and legal status can be verified."

The national focus on driver's licenses follows a stalled initiative requiring states to implement the tougher standards recommended by the 9/11 Commission. As the commission's report showed, Hani Hanjour, the hijacker who flew an airliner into the Pentagon, had four driver's licenses and ID cards from three states.

In Pennsylvania, PennDot began ramping up scrutiny of identity documents in 2003.

"Are they who they say they are? That is fundamental to the job that we do," Kurt Myers, PennDot deputy secretary for safety administration, said yesterday.

The four-hour meeting in Philadelphia, he said, was the second since May, when 2,100 Pennsylvania license holders - mostly immigrants - were notified that their licenses would be canceled within a month unless they produced valid Social Security numbers.

"Failure to comply shall result in the department referring this matter to the Pennsylvania State Police for prosecution," the notification letter stated.

Lawyers for the targeted drivers said the tight deadline and threatening tone provoked fear among immigrants. In a letter to PennDot, they stressed "the centrality of a driver's license in modern society" and said PennDot was being "unduly narrow" in its demands.

The department postponed its June 19 deadline pending further discussion.

At Wednesday's meeting of PennDot officials and immigrant advocates - including the Pennsylvania American Civil Liberties Union and the Philadelphia chapter of the American Immigration Lawyers Association - it was decided that a new letter will go out by the end of the month. Affected drivers will have 60 days to comply.

Pennsylvania law requires applicants to prove "legal presence" in the state before they can obtain a license or ID card. But in some cases, proof other than Social Security numbers can be accepted.

An example would be an immigrant here on a three-year, one-time-renewable, specialty worker's visa. His wife is legally in the country, too. But because her visa does not permit her to work, she does not get a Social Security number. Nonetheless, with appropriate documentation from U.S. Citizenship and Immigration Services, she should be able to obtain a driver's license.

PennDot also agreed to send the new letters in English and Spanish and to offer language support for other nonnative speakers.

PennDot spokeswoman Danielle Klinger said the May letter was the culmination of a process that began more than two years ago to root out fraud. The state vetted the identity data behind its 9.2 million driver's licenses by comparing the numbers in PennDot files against Social Security records.

Previously, she said, the numbers could not be verified electronically, so PennDot accepted any nine-digit number that a person presented.

After vetting, the number of nonmatches was pared to 45,000 and letters began going out in 2007 telling drivers they had to correct the problem or surrender their licenses. Of the first 43,000 notices sent, about 9,200 licenses were canceled, Klinger said, "either because people didn't have the required documentation or they chose not to respond."

Of the 2,100 people affected by the June letter, about 700 have provided the necessary documentation to keep their licenses, she said; 168 letters have been returned to the department as undeliverable.

Contact staff writer Michael Matza at 215-854-2541 or mmatza@phillynews.com.