MEMPHIS—While police have emphasized the possibility that missing Harvard professor Don C. Wiley committed suicide, Wiley’s family members said Saturday that investigators have told them there is no evidence besides his rental car—found abandoned on a bridge—to support that theory.

“I hate that suicide keeps getting brought up as the possibility rather than one of many,” Wiley’s sister-in-law, Susan Wiley, said in her home Saturday. “I just don’t think he committed suicide.”

Wiley, Loeb Professor of Biophysics and Biochemistry, was last seen at midnight Nov. 15 at the banquet for a scientific meeting in Memphis.

There were no signs of foul play when his car was found on the Hernando de Soto Bridge—over the Mississippi River—four hours later.

Memphis Police Department (MPD) Lt. Richard True, the department’s spokesperson for the Wiley case, said last week that based on past cases with similar evidence, “indications are [Wiley] parked the car on the bridge and took his own life.”

But Susan Wiley said that Sgt. Robert Shemwell, an investigator on the case, stressed to her after True’s comments were published that the MPD was treating the disappearance as a missing persons case rather than a suicide. The MPD prohibits investigators from commenting publicly, and recently directed supervisors on the case to reroute all inquiries to True.

Family and colleagues who saw Wiley right before his disappearance agree that his behavior was pleasant and unremarkable, and that he was at the pinnacle of his career.

Even if Wiley were suicidal, his brother Greg Wiley said, jumping off a Memphis bridge would be a highly unlikely method because the professor was “terrified of heights.”

Greg Wiley added that his brother was protective of their father—whose wife, Wiley’s mother, died last year—and would not have done something to cause him pain so close to the family’s hometown.

“He wouldn’t have done it in Memphis,” Greg Wiley said.

Wiley’s father, Bill Wiley, said the family had not yet decided whether they would hire a private investigator, but were considering the possibility.

But while the family doubts that Wiley took his own life, Bill Wiley said hope that his son is still alive is dwindling.

“We always hold out hope, but it’s down to five percent or so,” he said. “It’s been two weeks.”

According to True, tips to the department have spiked since the reward for “information leading to the arrest and charge” of anyone connected with the disappearance has increased.

The Howard Hughes Medical Institute, which has helped to oversee Wiley’s lab for the last two weeks, added $15,000 on Thursday to the $5,000 contributed by Harvard and $5,000 of private donations from members of the St. Jude Children’s Research Hospital in Memphis, which sponsored the banquet Wiley attended at the Peabody Hotel where he was last seen.