Detectives yesterday began questioning nine men arrested in connection with a so-called alleged kidnap terror plot in Birmingham – two days after police swooped.
Eight of the suspects were picked up in a series of dawn raids on Wednesday, while the ninth was stopped on a motorway in the city several hours later.
Police were on Thursday given a further seven days to hold the men after applying for an extension before Coventry Magistrates' Court.
Assistant Chief Constable David Shaw said a number of procedures had to be completed before formal interviews could take place.
"Far better that we use a measured, calculated, meticulous response than rush into things," he said.
Forensic specialists have been scouring 15 properties in Birmingham which were seized during Wednesday's operation. A further three search warrants were executed yesterday.
Mr Shaw said six searches had been completed and a "significant quantity" of exhibits have been gathered.
"I don't want you to read anything into that, you can imagine the sort of things that we will recover as part of the searches," he said.
"Our priority now is to examine what is actually contained in those exhibits."
The nine suspects, British men of Pakistani descent, have been detained on suspicion of the commission, instigation or preparation of acts of terrorism.
Mr Shaw said they will remain in custody at Chase Avenue police station in Coventry. Police can now detain terror suspects for 28 days without charge.
The alleged plot involved the abduction and beheading of a British Muslim soldier, according to sources. It has been suggested there could have been more than one potential target for the kidnapping.
Earlier, sources revealed that the establishment of a permanent SAS unit in London was prompted, in part, by the threat of a terror kidnapping similar to the alleged plot.
It emerged only a week ago that an elite unit had been placed on 24-hour stand-by in the capital to respond to a terrorist attack.
The threat of a "close quarters abduction" was one of the main reasons for moving a cadre of the crack troops to the capital, according to Whitehall sources.
The idea is that they would be able to carry out a "hostage release operation" within minutes of a target being seized.
"The authorities have decided that the kidnapping threat is now such that it is the most likely thing that is going to happen," a Whitehall source said.
The Ministry of Defence said it did not comment on the capability or tactics of the SAS.
However, a defence source said it was "no secret" that a number of special forces were posted in London and elsewhere.
There were claims yesterday that one or possibly two potential targets for the alleged kidnap plot were used in an extraordinary "tethered goats"-style operation.
They were put under round-the-clock surveillance but carried on their lives as normal as police officers continued their investigations, reports said.
There are also claims that at least two suspects are still on the run.