In the report on the arrest of Hunbal Akhtar, Mohammad Shoaib Mughal and Mohammad Shahid Hussain, the police said it had been established that the trio had links with Shahzad.
The investigators said the accused, who used to visit Pakistani Taliban chief Hakeemullah Mehsud, confessed in their statement made under Section 164 of the Criminal Procedure Code before a judicial magistrate that they provided $43,000 to Shahzad for the attacks.
Shahzad, son of a retired Pakistani air vice marshal, was sentenced to life in prison by a United States court last month.
Pakistani police said they had obtained the data of conversations between the accused and Shahzad. The anti-terrorism court of Judge Malik Mohammad Akram Awan adjourned the case till October 26 after receiving the report.
Investigators said in the report that Mughal allegedly allowed Shahzad and three other would-be suicide bombers to stay at his home for a week.
The police identified one of the bombers as Qaiser Mehmood and another as a brother of Taliban commander Qari Hussain. The identity of the third man was not known. The men who stayed at Mughal's house carried out suicide attacks in Muzaffarabad.
After the disappearance of Akhtar, Mughal and Hussain following Shahzad's arrest in the US, police believed they had been kidnapped and registered cases at different police stations of Islamabad and Rawalpindi. On September 5, they received information that they had gone underground and not been abducted.
The police reported that they arrested the trio from Islamabad Highway last month when they were travelling in a car while their two accomplices. The cops claimed a laptop and maps of important buildings of Islamabad, including the Parliament House, were found in the vehicle.
Investigators asked the court to convict the men for abetting and carrying out terrorist activities within and outside Pakistan.
However, reports have suggested that Akhtar, Mughal and Hussain were detained by intelligence and security agencies in May. Their formal arrest was made public last month after the security agencies completed interrogating them.