Local Mexican authorities have taken over the investigation, according to the State Department. The Mexican Tourism Board said in a statement obtained by CBS that "preliminary reports from local officials conclude that there were no signs of violence or struggle."
Ashli Peterson, a relative of the Sharps, posted about the family's disappearance on Facebook Thursday night, around the time that the family contacted police. The post was shared hundreds of thousands of times. On Friday afternoon, Peterson posted an update.
"Please respect the family at this time as they go through the grieving process," she wrote. "Thank you for all the posts, shares, and kind words."
Kevin Sharp was an avid stock car racer known as "The Sharpshooter" in the local racing scene, and he often competed in events in his neighboring county, Cliff Baldwin, his friend and fellow racer, told the Des Moines Register. He said he knew Sharp and his family his entire life, and that he and Kevin shared a love for the University of Iowa and the Kansas City Chiefs.
"He was a great personal friend," Baldwin told the Des Moines Register. "It's hard to talk about. The more I think about him and the family, the harder it is."
"Creston is close-knit like all small towns in Iowa," he added. "He's a big part of that community there."
Sharp and his family left the United States for Cancun, Mexico, on March 15, according to Peterson's post. The family then rented a car and drove to Tulum, where they were renting a condo, according to Amy Sharp's sister Renee Hoyt, who spoke with the Creston News Advertiser.
It was the family's second time in Mexico, according to Amy Sharp's cousin, Jana Weland, who told ABC News that the family had planned to meet up with some friends at a water park.
But "they never showed up at that water park to meet them," Weland said.
The Sharps were supposed to return to the United States about 2:45 p.m. Wednesday from Cancun and arrive in St. Louis at about 6 p.m.
From there, they would travel to Danville, Illinois, to attend Thursday's Southwestern Community College men's basketball game, Peterson said. The Sharps were avid Southwestern fans, and the college on Friday extended its condolences to their friends and family. Head basketball coach Todd Lorensen called the family "loyal, caring, supportive and generous."
"If our guys play that way we will be successful," Lorensen wrote in a Facebook post.
The Sharps had informed their family members on March 15 that they had arrived safely at their condominium in Tulum. So when family members didn't hear from them on Thursday - after they were supposed to have arrived in St. Louis - they became worried.
"We have filed a missing persons report through the US Embassy in Mexico already. We have also pinged cells phones and show that they are still in Mexico with no movement on their phones. Social media is also inactive," Peterson said in her Facebook post late Thursday night.
Hoyt, Amy Sharp's sister, told the Creston News Advertiser that Kevin Sharp's phone was tracked using Apple's Find my iPhone app, which it pinged in Mexico. The phone had not moved from its location since Thursday morning.
Relatives of the Sharp family could not be immediately reached for comment.
The family's mysterious deaths come amid increased travel warnings to Quintana Roo state, which is home to Tulum - a popular destination for those looking to explore Mayan ruins or snorkel in limestone sinkholes. The State Department issued a level 2 advisory to those traveling to Quintana Roo on March 16, meaning visitors should be cautious because of increased crime there. Department officials cited a spike in Quintana Roo's homicide rate since 2016.
Last month, the Milwaukee Journal Sentinel published an investigation that identified more than 150 reports from travelers who said they blacked out or became violently ill after having just one or two drinks at dozens of Mexican resorts in Cancun, Playa del Carmen, Puerta Vallarta and Los Cabos. It's unclear whether those tourists were deliberately drugged or became random victims of tainted alcohol, according to the investigation.
Another Journal Sentinel investigation from November looked at repeated instances where the travel and restaurant review website TripAdvisor removed posts warning of alleged rape, assault or other injuries at some Mexican resorts. And a July investigation into the death of a Wisconsin college student in Mexico uncovered widespread safety issues, including those tied to tainted alcohol, at Mexican resorts.
