Calcutta police announced the second "arrest" in the Audi hit-and-run case on Monday amid murmurs that Shahnawaz Khan alias Shanu had actually "surrendered", just like prime suspect Sambia Sohrab did on Saturday night.

A team of officers from the detective department knocked on the door of Mohammad Yusuf, a resident of Ajmer Sharif Gate in Delhi around 3am on Monday, and picked up his nephew Shanu. The young man, one of the suspects in the hit-and-run last Wednesday in which air force Corporal Abhimanyu Gaud was killed, didn't put up any resistance, the police said.

Sources in Delhi police said their Calcutta counterparts had informed the local police station about their plan to conduct the raid, but there was no request for assistance to locate the target.

"As part of protocol, a visiting police team needs to inform the local police before carrying out any raid in a city that is beyond their jurisdiction. Strangely, they did not ask for any details about the place where the accused was said to be hiding. A Calcutta police team rushed to the place on their own and arrested him," said a senior official of Delhi police.

"It seems they were familiar with the location or someone might have given them a fair idea of the place before reaching the capital," the official said.

Joint commissioner of police (crime) Debasish Boral said his team went to Delhi with "specific" information. "We arrested Shanu from his maternal uncle Mohammad Yusuf's home around 3am on Monday," he added.

Shanu was produced in a Delhi court later in the day and brought to Calcutta on an evening flight. When reporters asked Shanu at Calcutta airport who was driving the unregistered Audi Q7 when it knocked down Corporal Gaud, he replied: "Sambia."

Sambia is the younger of Trinamul leader and former RJD MLA Mohammad Sohrab's two sons. The police are looking for his elder sibling Ambia, who has also been missing since the incident last Wednesday.

Shanu was to spend the night at the Calcutta police headquarters in Lalbazar. Sources said he would be produced at Bankshall court on Tuesday.

Investigators have learnt that Shanu and Johnny, another friend of Sambia, had taken a bus to Kolaghat hours after the hit-and-run on Wednesday and proceeded towards Ranchi from there. Johnny and Shanu parted ways in Ranchi, with Shanu boarding the Gangasagar Express to reach Delhi two days ago.

Joint commissioner Boral declined to specify Shanu's involvement in the incident.

Shanu's brother Khalid had apparently accompanied the police team to Delhi, triggering speculation about how the cops could get a suspect's brother to accompany them unless everything had been "orchestrated".

A source told Metro that the "surrender" was negotiated through a youth named Amzad, who convinced Khalid to ask Shanu to give himself up.

Officers who interrogated Shanu said there were several inconsistencies in his statement. "Once Shanu is saying that he and Johnny rescued Sambia from the (accident) spot... then again he claims he had nothing to do with the incident," said a source.

The police said there was enough evidence to implicate Shanu. "We want to interrogate all three suspects together to sort out the confusion," an officer said.

The police on Monday also seized a white Skoda that they suspect was used by the driver of the Audi Q7 to flee the accident site. The investigation team had been looking for the vehicle since Shanu's sister-in-law Priyanka Khan submitted in writing that he was in a Skoda with Johnny and not in the Audi.

Officially, the police said they found the car abandoned somewhere in Topsia, but sources said the vehicle owned by Johnny's family was handed over to the cops through a lawyer as a "mark of cooperation". The Skoda is still registered in the name of a person named Anurag but was bought by Johnny's family earlier this year after the owner shifted base to Patna.