Pakistani police have arrested three people suspected to have been involved in Wednesday's attack on Prime Minister Yousuf Raza Gilani's motorcade, Geo TV channel reported on Thursday.
It quoted Tariq Kohsa, head of the investigation committee, as saying that the third car in the convoy was hit by a long-range rifle.
The report is expected to be submitted to the interior ministry soon.
Gunmen fired shots at the prime minister's motorcade in a high security zone on the Islamabad highway.
"The prime minister and his staff were not in the car," secretary to the interior ministry Syed Kamal Shah said.
A statement by the Prime Minister's House said that two shots fired at the prime minister's vehicle hit the window on the driver's side.
The outlawed Tehreek-e-Taliban Pakistan (TTP) Wednesday claimed responsibility for the attack.