Horst Skoff, a former Austrian tennis player who won four ATP Tour titles,  died during a business trip to Germany. He was 39.

Skoff died Saturday night in Hamburg and was initially diagnosed with heart failure, but his friend Arno Puckhofer said federal police had ordered an autopsy to determine the cause of death. Puckhofer told Austrian news agency APA that police were investigating why Skoff had injuries to his face.

"They don't necessarily have to be from the fall after possible heart failure," Puckhofer was quoted as saying.

Puckhofer said Skoff, who ran a tennis school the past 19 months, battled weight problems since his retirement from the sport in 1995.

Skoff was ranked as high as 18th in the world in 1990, and had a singles record of 228-203. He also added two ATP Tour doubles titles to his four singles victories.

Skoff helped lead Austria to the 1990 Davis Cup semifinals along with the former top-ranked Thomas Muster. Austria lost 3-2 against the United States in front of 40,000 spectators at Vienna's Prater Stadium, after Skoff lost a five-set match to Michael Chang.

One of Skoff's most memorable victories was a five-set win over the former top-ranked Mats Wilander in the 1989 Davis Cup quarterfinals, in a match that lasted more than six hours.