Another two men have been arrested following the death of a policeman in a suspected hit-and-run collision, Scotland Yard said.
The pair - aged 19 and 23 - were held on Monday night, hours after a man was remanded in custody accused of causing death by dangerous driving and failing to stop at the scene of an accident.
The defendant, who was charged under the name Gary Bromige, but appeared in court under the name Gary Cody, was further charged with failing to report an accident and driving without insurance.
Pc Andrew Duncan, 47, was struck by a car in the early hours of Friday while working on speed checks in Sutton, south London. The married father of two died in hospital on Sunday morning.
Two men aged 19 and 20 were arrested that day and bailed until a date in October. A woman who was arrested on Saturday on suspicion of perverting the course of justice has also been bailed.
Officers were questioning the second 19-year-old and the 23-year-old on Monday night.
A Scotland Yard spokesman said: "Detectives investigating the death of Pc Andrew Duncan following a collision in Sutton have arrested two further men.
"The men are currently in custody at a south London police station."
Metropolitan Police commissioner Sir Bernard Hogan-Howe hailed Pc Duncan as a "hard-working and courageous policeman" following his death. "The night he was injured he was doing a job that he loved and we all had every right to expect he would return safely to his home and family - tragically that was not the case," he said.
Pc Duncan joined the Metropolitan Police in 1990 and was originally posted to Battersea. He had been a member of the south west traffic unit for nearly 10 years.