Anti-terrorist police searched two more houses in Gloucester on Friday, while continuing to question a local man.
Sajid Badat studied in Blackburn, Lancashire
Police were at the properties for two-and-a-half hours, but said "nothing of significance" had been found.
Sajid Badat, 24, was arrested in the same area under the Terrorism Act on Thursday, and is being held in London.
In a separate development, it emerged later on Friday that a 33-year-old man was arrested under the Terrorism Act in Birmingham on Thursday.
Police were searching three homes and three businesses in the city on Friday night, following the man's arrest.
Meanwhile a 39-year-old man taken into custody in Manchester in another separate anti-terror investigation was released.
Police are not linking any of the three operations.
In Gloucester, officers are still searching Mr Badat's home and another nearby flat.
Police said they may still search other properties in the city.
The two latest houses to be searched, one in Derby Road and the other in All Saints Road, were unoccupied at the time.
BBC correspondent Andy Tighe, speaking from Scotland Yard, said it was important to remember that Mr Badat could be released without being charged with any terrorist-related offences.
He said 481 people had been arrested under the Terrorism Act since it was passed in 2000, but only 75 had been charged.
Under the act, police are permitted to hold suspects for up to seven days before deciding whether charges should be brought.
Earlier Scotland Yard said a "relatively small amount" of explosive materials had been removed from Mr Badat's house in St James Street after it was searched on Thursday.
Gloucestershire Police's Inspector David Peake said the other occupants were now in a "safe house" away from their home, which was still being looked at by forensic experts.
In the search of the second flat - which is still continuing - police said no arrests had been made and the street was not sealed off.
Mr Peake said no explosives and "nothing significant" had been found at that address - a flat above a shop on Barton Street - but the property was being checked over by forensic experts.
Mr Badat is being questioned at the high-security Paddington Green police station in west London.
Residents of 119 homes were evacuated on Thursday as police searched Mr Badat's house. They returned home on Thursday night and the street remained open on Friday.
Officers have dismissed as "pure speculation" reports that a suicide attack was being planned on a football stadium.
Mr Badat had been under surveillance by the police and the security service MI5.
The arrest came as part of a joint anti-terrorism operation between the Metropolitan and Gloucestershire police forces.
Whitehall sources confirmed they had been checking on possible links he has with "shoe bomber" Richard Reid, who was sentenced to life for trying to blow up a US passenger plane.
Police also searched two addresses in Blackburn as part of the operation. One was the College of Islamic Knowledge and Guidance, where Mr Badat used to study.
Ibrahim Master, chairman of the Lancashire Council of Mosques, said religious leaders had been "fully co-operative" in the search.
"Islam prohibits the loss of innocent lives and as such we condemn all acts of terrorism, whether it's here in the UK or anywhere else in the world," he added.
Neighbours spoke of their shock to discover Mr Badat was the man arrested in Gloucester.
The owners of nearby Bismallah Butchers said Mr Badat he was a good Muslim man, extremely bright, mad on football and a "walking angel".
Thursday's arrests came a week after double suicide bombings in Istanbul in which at least 28 people died.