A 100m cordon was put in place when the vehicle was discovered near Banff Road, where suicide bomber Salman Abedi had visited in the days before the attack on Manchester Arena.
U.S. pop star Ariana Grande, whose concert was targeted in the attack, has arrived in the United Kingdom ahead of a benefit show in Manchester on Sunday.
Detective Chief Superintendent Russ Jackson, head of the North West Counter Terrorism Unit, said: "This is potentially a significant development in the investigation". "We have had police officers conducting house to house enquiries but we are still not satisfied why Abedi went there and its vital we understand exactly where he went there and who he spoke to in these final days before the attack".
As a precaution, people were being evacuated from the nearby Ronald McDonald House, which offers accommodation for families with children who are being treated in the hospital.
The developments came as "unscrupulous" ticket touts attempted to profit from Ariana Grande's One Love Manchester gig to raise money for the victims.
A Royal Logistics Corp bomb disposal team was called to the area on Friday and forensics officers were also at the scene.
"Manchester's strength and togetherness is an example to the world", he wrote in a book of condolence.
Greater Manchester Police have confirmed a terrorist attack has killed at least 22 at the MEN Arena as concertgoers were leaving an Ariana Grande show.
Police say the 22-year-old bomber, Salman Abedi, acted largely alone when he assembled the device used in the May 22 attack.
Abz Forjani said: "I am just still in shock to be honest about what has happened".
Isaac, 24, and Abz Forjani, 21, were arrested by police after the suicide bombing and questioned for a week. She had suffered a concussion and some crush injuries.
Isaac, 24, said: "It's not easy being connected to 22 lost, innocent lives".
"And the fact that the person that did this is related to us by blood".
"I eventually met her in a hotel in the early hours of the morning", Buckley said.
Ten men, aged between 18 and 44, remain in custody on suspicion of terrorism offences in connection with the attack, police have said.
Six people, including a 15-year-old boy, have been released without charge.