Washington: Police and aviation authorities in Florida's Miami-Dade are scouring a swampy grassland for clues to help explain what caused the midair collision between two small aircraft in which an Indian woman trainee pilot and three others were killed.

The body of the fourth victim of the midair collision between the two small aircraft of a Miami flight school over a swampy grassland was retrieved yesterday, ending the mission to look for survivors, the Miami Herald reported. But searchers continued to scour the razor-like sawgrass in hopes of finding clues to help explain what caused the accident, the daily said.