On Wednesday, police said the two were among 14 suspects held late on Friday during an investigation into a suspected terrorist-training network.
Police have searched an Islamic school in East Sussex and 17 homes in London as part of their investigation.
A police source told Reuters on Saturday that the operation focused on the suspected training and recruitment of terrorists.
"In all operations, some people may be released early without charge while others may remain in custody for further investigation," the unnamed police source said.
Police are holding 12 others. The police have warrants to hold three until Wednesday and the remaining nine until Friday, by which time they must charge, release or seek more time to question them.