Two of four men arrested on suspicion of spying for Iran have been released without charge.
The four were arrested on 6 March on suspicion of assisting a foreign intelligence service, relating to Iran.
The investigation relates to the surveillance of locations and individuals linked to the Jewish community in the London area.
A warrant for their further detention was granted on 12 March, allowing for them to be detained in police custody up until 20 March.
On Sunday, one of the men was released from custody without charge.
Another man has also been released without charge, said police.
Two men, a 40-year-old and a 22-year-old, arrested in the Barnet and Harrow areas respectively, remain in custody.
Read more:
Three arrested after man's body found in wheelie bin
Nursery worker who abused toddlers jailed
Deputy Assistant Commissioner Vicki Evans, senior national coordinator for Counter Terrorism Police, said: "This has been a long-running investigation, and part of our ongoing work to disrupt malign activity where we suspect it.
"We fully recognise that the public - and in particular the Jewish community - may be concerned, but I also hope the action we have taken reassures them that we will not hesitate to take action if we think there may be a threat to their safety.
"As ever, I would ask them to remain vigilant and if they see or hear anything that concerns them, then to contact us."
(c) Sky News 2026: Two of four men arrested on suspicion of spying for Iran released without charge
Meningitis: The symptoms, treatments and how to find out if you need the vaccine
Nursery worker who raped and abused toddlers jailed
Three arrested after man's body found in wheelie bin
Kent meningitis outbreak a cruel reminder young people are most at risk
Dubai airport shutdown affects thousands of UK passengers as drone strikes fuel tank
Two schools in Cardiff closed after online weapons threats, police say
King hits the decks to try his hand at DJing in Manchester
Chelsea given record £10.75m fine and suspended transfer ban over secret payments
