(CNN) -- Bulgarian police have widened their investigation into last week's bombing attack on Israeli tourists to towns near the border with Romania, asking hotels for surveillance video that might have captured the suspected bomber.
Hotels in the Black Sea coastal city of Varna say police have been asking for video showing a particular suspect and are giving a sketch of the suspect to management.
Investigators also have questioned workers at a car rental agency near the Black Sea coast where the man attempted to rent a car before Wednesday's attack, the agency's owner told CNN.
Five Israeli tourists were killed and more than 30 other Israelis were wounded when a suicide bomber blew apart their bus at Burgas International Airport.
Bulgarian authorities still have not been able to identify the bomber, who was seen on airport security videos about an hour before the attack. They have taken fingerprints and DNA samples and given that information to their counterparts in Israel, the United States and Interpol.
The Bulgarian Interior Ministry says it is not ruling out the possibility that the suspect had help, though it won't comment on reports that authorities are looking for a second suspect.
The owner and an employee of the Afrodita Car Rental Agency told CNN a suspicious man wanted to rent a car the Sunday before the attack and tried to use the Michigan driver's license later found at the scene of the attack.
When the owner said he wanted to photocopy the license, the man grew nervous and refused to have it copied. At that point, the owner said he refused to rent the man a car and the man walked out.
The car rental owner described the man as having short dark hair and speaking English with an accent. The woman who conducted the forensic reconstruction of the suspected bomber's face and body, told Bulgarian TV the man had a white face, light eyes and thick dark hair.