Tournament organisers said transport operations had returned to normal in the early hours of Sunday.
A statement from Birmingham 2026 read: "Birmingham 2026 can confirm that transport operations have returned to normal following a police incident on Saturday evening.
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"Championship transport was suspended until the necessary security measures had been carried out whilst West Midlands Police arrested a man in his thirties on suspicion of fraud.
"The safety and wellbeing of our spectators, athletes, workforce and the wider Championships' family will always be our first priority.
"We recognise that the delays presented challenges for those affected and would like to thank everyone for their patience, understanding and cooperation throughout the evening.
"Further information will be issued on Sunday relating to the evening's postponed medal ceremonies."
A West Midlands Police spokesperson confirmed that a man in his 30s was arrested on suspicion of fraud and remained in custody for questioning.
The crowd at the Alexander Stadium appeared to be near its 23,000 capacity to watch Saturday's evening session, which concluded with Great Britain winning a pair of gold medals in the men's and women's 4x100m relays.
At one point during the session, there was an announcement that the six medal ceremonies, scheduled to take place after the final event between 10pm and 11pm, were cancelled.
The Press Association understands this decision was taken in relation to the police incident.
Outside, there was a visibly heavy police presence and huge static queues of people waiting for shuttle buses.
