Investigation
A panel that the government had formed, consisting of police officials and experts from security agencies to probe the attack, presented a preliminary report to the Prime Minister. The Interior Secretary Syed Kamal Shah also admitted to the Senate's Standing Committee on his ministry that the blast was the result of a defective security system. He added that the Islamabad police chief has said intelligence agencies had informed the police about an explosive-laden vehicle entering the city to carry out an attack.
Three suspected terrorists Mohammed Aqeel (possibly Dr. Usman), Rana Ilyas and Hameed Afzal were arrested in Peshawar on 17 October by the Pakistani police with connection to the attack were remanded to police custody for 7 days on 18 October for questioning by an anti-terrorism court. They were suspected of having facilitated the suicide bomber. In requesting the court for a 10-day remand, the police also said they hoped to arrest more suspects with information from the three. Judge Sakhi Muhammad Kahut, who remanded the trio to police custody, also ordered police to produce them in court again on 24 October.
Another Dr. Usman, possibly the same man, went on in 2009 to take part in the attack on the Sri Lanka national cricket team and the raid against the Pakistani Army Headquarters.
Police Qari Ishtiaq, who is said to the commander of Punjabi Tehrik-i-Taliban. He was arrested from Bahawalpur on the information provided by the Hijratullah who has been jailed for 10 years due to his rôle in Lahore police academy attacks. Seven other militants were arrested from different parts of Punjab regions on his information him. Four hundred kilograms (880 lb) of explosives were also seized from Qari Istiaq.
On 5 May 2010, Mohammed Aqeel, Rana Ilyas, Muhammad Hamid Afzal and Tahseen Ullah were acquitted of all charges as no evidence was ever presented against them.
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