Everard, 33, was last seen a week ago, as she walked from a friend’s house in South London to her home near Clapham Common.
On Tuesday night, the Met police announced that they had arrested one of their own in relation to her disappearance, along with a woman who is suspected of assisting an offender.
The officer was not on duty at the time Everard went missing, police said.
“The arrest this evening is a serious and significant development,” Assistant Commissioner Nick Ephgrave said in a statement. “We will continue to work with all speed on this investigation but the fact that the arrested man is a serving Metropolitan Police officer is both shocking and deeply disturbing.
“I understand there will be significant public concern, but it is essential that the investigative team are given the time and space to continue their work.”
Detective Chief Inspector Katherine Goodwin said it was a significant development in the investigation.
“We have seen an overwhelming response from the public and I repeat my request for anyone with information that may be relevant to come forward, no matter how insignificant it may seem,” she said in a statement.
Police released another picture of Everard yesterday. They had previously released a number of other photos of the woman, taken on the evening by CCTV cameras and on previous occasions.
Everard’s route home has been the focus of investigations, with police officers searching streets and nearby areas, including Clapham Common.
Police say she had been at a friend’s house on the evening of Wednesday, March 3, before leaving at around 9 p.m. on what should have been a 50-minute walk to her home in Brixton via Clapham Common.
She has not been seen or heard from since.
She was last seen on CCTV around half an hour later walking in the direction of Tulse Hill.
Police are encouraging motorists who passed through the area at that time to check their dashcam footage.
“We have seized a number of CCTV recordings but we know that there are likely to be many more out there,” Goodwin said.
“Please, even if you’re not sure, check your doorbell or CCTV footage just in case it holds a clue. I’m also asking delivery drivers or anyone with dashcam footage who would have been in the Poynders Road area at approximately 21:30hrs on Wednesday to come forward.”
Reuters contributed to this report.