Authorities are investigating after a mail carrier was attacked and seriously injured Tuesday morning in Medford. 

Medford police said officers responded about 11:40 a.m. to a 911 call reporting the assault in the area of Arden Road at Winthrop Street. At the scene they found a United States Postal Service letter carrier, suffering from apparent facial injuries, who told officers he was assaulted by three individuals while on his route. The suspects allegedly took a post office key from the postal worker and then fled toward Playstead Road to a waiting vehicle. 

The letter carrier was taken to the hospital with serious injuries.

Police said the suspect vehicle was later located in Lowell and a number of people in it were identified. No arrests have been made, but police said the investigation, which is being undertaken in conjunction with the United States Postal Inspection Service, remains “extremely fluid and ongoing.”