These observations were made in an interim report submitted by Punjab's provincial police chief Javed Iqbal to the Supreme Court, which is hearing a case related to Shahzad's murder.
None of Shahzad's friends, colleagues or family members have provided any specific information that might pinpoint suspicion regarding an individual, said the report, a copy of which was accessed by PTI from sources in the Punjab government.
"So far the investigation has not yielded any lead that could help narrow down the scope of the investigation and bring into sharp relief any possible suspect(s)," the report said.
The report said the investigation has been greatly hindered by the non-availability of any of the electronic gadgets used by the Shahzad, including his cell phone.
Efforts to access Shahzad's email account have not met with any success, it said.
The analysis of the call data record of Shahzad's mobile number is an ongoing process and callers of telephone numbers provided so far have largely been identified, the report said.
No specific information could be culled that might provide any lead about the perpetrator until now, it added.
The slain journalist was being monitored and the perpetrators knew his timings, route and routine, the report said. He was picked up from a secure area.
Shahzad went missing while driving from his home to a TV station in Islamabad on May 29, two days after he alleged in an article that al-Qaeda had infiltrated the Pakistan Navy.
His body was found the next day in a canal at Mandi Bahauddin in Punjab, some 200 km from Islamabad.
Punjab police chief Iqbal said in the report that the investigation was underway and it would be finalized purely on merit and in accordance with the law.
The report mentions different types of evidence collected by police and statements given by the family and colleagues of the slain journalist.
The report stated that Mudassar Hamza Amir, who lodged the First Information Report about Shahzad going missing in Islamabad, had commented on his (Shahzad's) "sterling character and professionalism".
Amir said many quarters would possibly have been irked with Shahzad who wrote about issues "truthfully and bluntly".
Shahzad's reporting largely focussed on the war on terror and Pakistani militant groups. The report noted that there was a mention in a news report in the Dawn newspaper on June 1 of an email sent by Shahzad, in which he had named the ISI for harassing him.
Police chief Iqbal said he did not want to implicate anyone without any evidence and the investigation agencies might need to explore all possibilities.
Muhammad Faizan, an Islamabad-based senior reporter and a childhood friend of Shahzad, said the slain journalist had no animosity with anyone.