Patna, Jan 19 (IANS): Bihar DGP S.K. Singhal said on Tuesday that contract for airport parking lot could be the reason behind the murder of IndiGo state head Rupesh Kumar Singh, who was allegedly shot dead by criminals near the Shastri Nagar police station area in Patna on Januray 12.

"We are investigating the case from all possible angles. Prima facie, it appears that contract for airport parking lot could be the reason behind the killing. Whoever was behind the conspiracy had hired contract killers from outside the state," Singhal said.

Earlier, Singhal briefed about the investigation to Chief Minister Nitish Kumar, who is closely monitoring this case.

Singhal pointed out that there was a dispute over the airport parking lot and the deceased was involved in it. Some of the deceased's family members and relatives are involved in private and government contracts.

"The investigation has reached a decisive phase and we will soon disclose the facts after the arrest of the conspirators," Singhal said.

"We are thoroughly probing every government and private contracts obtained by the relatives of Singh. This case is extremely complicated and sensitive," he said.

Singh was killed on January 12 at around 7.15 pm when he was returning from the Patna airport. As soon as he reached the gate of the his residential complex in Punaichak, unknown assailants shot him from close range, killing him on the spot.