Updated

Authorities in northwest Mississippi are urging drivers to use caution when approached by any vehicle with flashing blue lights as investigators search for who was responsible for two highway killings.

On Monday, authorities said two people shot along highways may have been killed by someone who posed as a police officer and pulled them over late at night.

DeSoto County Sheriff Bill Rasco says efforts are focused on keeping motorists safe while investigators chase leads that are pouring in. He said many tips involve suspicious vehicles. So far there have been no arrests.

Rasco says motorists can call 911 if they are being pulled over. He said agencies can quickly determine whether they have vehicles in the area and dispatch help if needed.