The Lawrence Bishnoi angle is also being investigated.
Baba Siddique only had non-categorised security and three policemen had been assigned to him for his protection, the Mumbai Police said on Sunday, a day after the former Maharashtra minister was shot dead outside the office of his son, MLA Zeeshan Siddique, in Bandra East.
Addressing a press conference, Deputy Commissioner of Police (Crime Branch) Datta Nalawade also said one of the police personnel was with Siddique, who is a member of the Ajit Pawar faction of the NCP, when he was shot around 9.30 pm on Saturday.
"A case was registered and the investigation was handed over to the Crime Branch. After the firing, police personnel at the spot showed courage and arrested two accused while one managed to escape. We have got the custody of one of the accused till October 21. Two pistols and 28 rounds have been recovered," the police officer said.
To a question on whether Mr Siddique had Y-level security as was initially reported, Mr Nalawade said he had non-categorised security and three police personnel had been assigned for this purpose.
The accused who have been arrested have been identified as Gurmail Baljit Singh from Haryana and Dharamraj Kashyap from Uttar Pradesh. Police are looking for the third shooter, Shiv Kumar Gautam, who is also from Uttar Pradesh.
Mr Nalawade said they are looking into the records of all accused and are also in touch with their colleagues from the hometowns of the accused.
"We are investigating when the accused came to Mumbai, where they were living and who harboured and financed them," he said.
Earlier on Sunday, the Lawrence Bishnoi gang had taken responsibility through a post on Facebook by one Shubuu Lonkar, believed to be Shubham Rameshwar Lonkar, an associate of the Lawrence Bishnoi gang. In the post, Lonkar claimed that Siddique had been killed because he was linked to India's most wanted terrorist Dawood Ibrahim, was close to Salman Khan and because of the death of Anuj Thapan, one of the arrested suspects in the shooting outside Mr Khan's house in April, in police custody.
When Mr Nalawade was asked about this, he said the post and the Lawrence Bishnoi angle are being investigated.
Security has been tightened around Salman Khan's house, Galaxy Apartments, in Bandra. A tight security cordon has also been put in place in South Mumbai's Malabar Hill, where the residences of Chief Minister Eknath Shinde and Deputy Chief Ministers Devendra Fadnavis and Ajit Pawar are located. Siddique, who had been part of the Congress for 48 years, had switched to Mr Pawar's party earlier this year.
(With inputs from ANI)