A 26-year-old man is being questioned by police after being arrested on suspicion of murdering a company director who was shot in the neck during an armed raid.
West Midlands Police said the suspect was detained at a property in Leicester on Friday night by detectives investigating the death of Birmingham businessman Akhtar Javeed.
A police spokesman said a 19-year-old woman had been arrested on suspicion of assisting an offender, while an 18-year-old man arrested in Derby on Thursday remains in custody.
The female suspect was also arrested in Leicester at the same address as the 26-year-old man.
Detective Chief Inspector Martin Slevin, who is leading the inquiry, said: "This is a fast-paced investigation and further arrests have been made as we continue to investigate Mr Javeed's murder.
"I continue to appeal to people to come forward. I firmly believe that someone out there may still have information that could help our investigation and I am urging them to call me or one of my team."
Mr Javeed, who lived in east London, was among five staff members who were tied up by masked men at his soft drinks distribution business in Rea Street South, Digbeth, on February 3.
The 56-year-old father-of-four is believed to have been trying to fight back when he was shot.
Detectives have seized a silver Renault Megane as part of the inquiry, having appealed for sightings of a car seen leaving Rea Street South with its lights off shortly after the shooting.