WASHINGTON (AP) — Two laptop computers with detailed personal information about commercial drivers across the country who transport hazardous materials are missing and considered stolen.

The laptops belong to a contractor working for the Transportation Security Administration and contain the names, addresses, birthdays, commercial driver's license numbers and, in some cases, Social Security numbers of 3,930 people, according to an Oct. 12 letter from TSA to lawmakers.

The contractor told TSA that the personal information was deleted from the computers before they were stolen, the letter stated. But after the second laptop was stolen, TSA investigators discovered that a person with data recovery skills could recover the personal information that the contractor deleted.

News of the security breach came the day before TSA begins collecting similar personal information from employees with access to areas at the port of Wilmington, Del. The Transportation Worker Identification Credential program is set to launch in Wilmington on Tuesday. Eventually 750,000 employees across the country with access to port areas will be required to submit information for background checks.