Authorities in Houston are searching for a woman who was last heard from Sunday after she became trapped in an elevator as floodwaters inundated the city, according to multiple reports.

>> Read more trending news

Jill Renick, 48, checked into the Omni Houston Hotel with her dog Saturday before the city flooded, KHOU reported. She worked as the spa director for the hotel, at Riverway and South Post Oak Lane, according to KPRC.

"She couldn't walk away," Pam Eslinger, Renick's sister, told KHOU. "The place was flooded. At final point there, it was 20 feet underwater in the lobby."

She told the news station her sister’s last known conversation was with one of her co-workers, “saying, ‘I’m in an elevator. The water is rushing in. Please help me.’”

"(I) don't know if she got out," Eslinger told KHOU. "My thought is that she probably didn't."

Authorities have found Renick's dog and car at the Omni Hotel, according to the Houston Chronicle, but there has been no sign of Renick.

"The unknown is absolutely killing us right now," Renick's nephew, Austin Miller, told the Chronicle. "I haven't stopped thinking about it."

Authorities told KHOU that they were investigating reports of a body in the basement, although it wasn't clear whether the body was Renick's. Gary Norman, spokesman for Houston's Office of Emergency Management, told the Chronicle on Wednesday that search efforts were hampered by the depth of the floodwater in the hotel, which was also contaminated with oil and gas.

"Of course, I'm hoping she's still alive. I'm hoping that we find her soon," Eslinger told KHOU. "As every minute ticks by, I'm still trying to keep the faith. I just want her back."

In a statement released to KPRC, an Omni Hotel representative said the company's employees are working with authorities in an effort to find Renick.

“We pray our associate will be located safe and unharmed,” the statement said. “In the meantime, our thoughts and prayers go out to our associate’s family during this difficult time.”

More than 30 people have been killed as a result of Harvey, which made landfall on the coast of Texas late Friday as a Category 4 hurricane.

Hurricane Harvey: Flooding and Aftermath