This may have enabled them to obtain warrants for further detention.
In London, in 1986, 101 warrants of further detention were sought; 100 were granted.
Short of a sharp turn, Ai is unlikely to face further detention in this case, but he is hardly out of the woods.
He was soon overtaken nevertheless, and again surrounded, but without further detention was then permitted to go down to the sea.
For further detention, a court must order the imprisonment.
Ms. Hemming said the authorities had not decided whether to seek the further detention of any of the suspects still being held without charge.
At the 36 hour point the suspect must be charged, released or an application made for a warrant of further detention.
The warrant can authorise further detention for periods up to 36 hours.
One factor offered as a justification for his further detention stated:
"Taking all the above factors into consideration," it said, "we do not believe that due process can tolerate any further pretrial detention in this case."