Police in Los Angeles are investigating whether the city's paparazzi commit criminal conspiracy in order to gain photographs of celebrities in distress.
LA police said some photographers 'crossed the line' into crime
Photographers have reportedly teamed up to provoke stars, then captured their reactions on film.
Los Angeles County district attorney William Hodgman said: "Somebody's going to get hurt or killed because of this."
Last week, US actress Lindsay Lohan was hurt when photographer Galo Cesar Ramirez allegedly drove into her car.
"In certain, specific incidents, the paparazzi have crossed the line into criminal behaviour," said Mr Hodgman, who launched the investigation before Lohan's accident on 1 June.
"We are aware of numerous instances where the children of celebrities have been jeopardised by the conduct of the paparazzi."
Most traffic law violations and petty crimes committed by photographers in pursuit of lucrative celebrity pictures carry relatively little legal risk by themselves.
But collaboration could increase the severity of the crimes.
Los Angeles police said they were investigating individual photographers as well as the agencies who paid for their work.