Reuters reports that two small aircraft collided mid-air about 15 miles southeast of downtown San Diego on Sunday, killing at least four people and starting a two-acre brush fire.

“There are four confirmed fatalities,” Cal Fire Division Chief Nick Schuler told CNN. “There could be more.”

Authorities say the planes were attempting to land at Brown Field, a municipal airport about 1.5 miles north of the Mexican border, when they crashed into each other at around 11 a.m. From KSWB:

Cal Fire identified the planes as a twin-engine Saberliner and a single- engine Cessna 172. The death toll was originally reported as two, then three, then four, as the afternoon wore on and grisly discoveries were made.

Firefighters from San Diego, Chula Vista and Cal Fire worked on the crash aftermath and rash of brushfires. One firefighter, from Chula Vista, was taken to a hospital for treatment of heat exhaustion, Cal Fire said.

“There is (a) fairly large crash scene,” San Diego Fire Department spokesman Lee Swanson told CNN. “There is debris scattered about a quarter of a mile.”

[Image via San Diego Fire Department]