Falling out of love.

BRUSSELS, Belgium ?- Authorities have opened a murder investigation into the death of a sky diver, saying they believe someone tampered with her parachute in an apparent fight over a lover.

Els Van Doren, 37, fell 13,000 feet to her death last November after her parachute and emergency chute failed to open.

A fellow female sky diver was detained for questioning last week and is the "prime suspect" in the investigation, prosecutor Michel Zegers said yesterday. No charges have been filed.

Investigators believe Van Doren and the suspect, who belonged to the same parachute club, also dated the same man, a Dutch national identified as "Marcel."

News reports say the suspect killed Van Doren in a jealous rage after learning Van Doren had an affair with her boyfriend.

"I believe we can call this a crime of passion," Zegers said.

A court date is set for Feb. 16 in the eastern city of Tongeren to assess the evidence.

Van Doren had jumped from a plane with three others, including the suspect and the Dutch boyfriend. She crashed to her death at 130 mph near Opglabbeek, a small town in central Belgium.