The collision, between a Ford Focus and an Audi A7, took place on the A456 at Callow Hill at around 10.15pm on Wednesday.
Three people in the Ford Focus - a 32-year-old woman, a 28-year-old woman, and a four-year-old boy - were pronounced dead at the scene.
Three people in the Audi also suffered minor injuries, and were taken to the Worcester Royal Hospital.
After the crash, police arrested three men aged 31, 25, and 18, as well as a 17-year-old boy. They have since been bailed pending further enquiries.
Police have recovered two other vehicles which they believe to have been involved, including a silver Volkswagen Golf and a black Vauxhall Vectra.
The crash has sent shock waves through the Midlands and beyond at the tragic loss of life.
One tribute posted online read: "So terribly sad, heartbreaking news for family and friends who have lost their loved ones.
"There are no words to say that will ease the pain of such devastating loss. My thoughts are sent to everyone involved."
People with information have been asked to contact investigation team at West Mercia Police on 101 extension 773 2145, or by email at firstname.lastname@example.org.
To share information anonymously, contact Crimestoppers on 0800 555 111 or crimestoppers-org.uk.