BRATISLAVA, Aug. 20 (Xinhua) -- Seven people were killed - two pilots in one plane and two pilots and three skydivers in another - in a collision involving two small aircraft near the village of Cerveny Kamen in Western Slovakia on Thursday.

Slovak Interior Minister Robert Kalinak, at an improvised briefing near the crash site, said: "All of the 35 skydivers on board the two downed airplanes that collided mid-air during a skydiving rehearsal attempted to parachute to safety but three of them didn't succeed. An investigation will reveal the reason why they weren't able to save themselves."

There were two pilots and 17 skydivers on board each plane.

"Shortly after take-off and the first aerial maneuver, there was an as-yet unexplained collision, after which they subsequently began to drop from the sky," said Kalinak.

"It's a terrible disaster, especially considering they were rehearsing a synchronized sky dive to bring joy at an air show that was set to take place in a couple of days," he said.

According to Juraj Gyenes from the Slovak Aviation and Maritime Investigation Office, the cause of the accident is still unknown. One of the planes dropped sharply and hit the other one shortly after taking off, he added.

Ambulance operator Falck spokesperson Alena Lacykova-Krcova said: "Of the total number of 31 survivors, six skydivers were recommended for transportation to hospital, but two of them refused."

More than 200 firefighters, rescuers and police officers are searching the area to find the evidence for the investigation. At the moment, the bodies are being identified.