A young boy had been killed in a crash involving an off-road bike and a car in Newark.
The four-year-old was a passenger on the bike which struck the vehicle in Churchill Drive on Sunday evening, shortly before 6pm.
Police said the bike was travelling in convoy with a second bike, whose rider left the crash scene before officers arrived.
A 24-year-old man riding the bike the boy was on suffered serious injuries and has been taken to hospital.
He was arrested by Nottinghamshire Police on suspicion of causing death by dangerous driving.
Following further inquiries, a 32-year-old man was arrested on Monday on suspicion of causing death by dangerous driving.
Officers are urging anyone with any other information, or relevant dashcam, mobile phone, CCTV or doorbell camera footage, to contact them.
Detective Inspector Jamie Moore said: "This is a tragic incident and our thoughts are with the boy's loved ones at this incredibly distressing time.
"They are being supported by specialist family liaison officers and kept informed about the investigation.
"As we learn to understand exactly what happened, I'd urge anyone who can assist with information or footage to contact police without delay."
Anyone who can assist should call 101, quoting incident 449 of 30 August 2026, or Crimestoppers anonymously on 0800 555 111.
