The son of Italian fashion mogul Vittorio Missoni says a plane crash is the "least plausible" explanation for his father's disappearance off the coast of Venezuela, hinting that he might have been kidnapped.
Venezuelan authorities have been searching since the twin-engine plane was lost Friday near the resort islands of Los Roques. On board were Missoni, three other Italians -- including his wife -- and two Venezuelan crew members.
Missoni's oldest son, Ottavio, told Italian newspaper Corriere Della Sera Wednesday, "A plane cannot vanish in this way, on a short route, without leaving any trace. I remain convinced that the least plausible reason is that they crashed into the water."
His opinion is based on a mysterious text message apparently sent from the cellphone of Guido Forsti, who was on the plane, to Forsti's son more than 48 hours after it disappeared.
Missoni told the newspaper the text message read, "Call now. We are reachable."
Missoni said he has even reached out to his father's potential enemies in search of any explanation.
Venezuelan officials said more than 400 people in boats, planes and helicopters searched Wednesday for a sixth day without success. No wreckage or debris has been found and Venezuelans will suspend the search after today.
An Italian team that assisted in search efforts last year with the Costa Concordia shipwreck is set to arrive in Venezuela later today to help.
"It's really hard to believe the airplane isn't in the water," John Nance, the ABC News aviation analyst, said. "By the same token, unless you find wreckage, there's no proof it hasn't flown off someplace else. But I find that hard to believe."
Asdrubal Bermudez, the owner of the plane, told The Associated Press in a telephone interview Wednesday that the plane was flown by an experienced pilot and its maintenance was up-to-date. Bermudez said he has no idea what might have gone wrong, and noted that there was no contact between the pilot and air traffic controllers when the plane dropped off radar.
Corriere Della Sera published the last known image of Vittorio Missoni and his friends moments before they boarded the plane in Los Roques Friday bound for Caracas.
Thirty minutes after takeoff, the plane vanished into the Caribbean, leaving the tight-knit Missoni clan anxiously waiting for answers.
Missoni, 58, who runs the family business with his siblings, Luca and Angela, has been instrumental in bringing the brand to luxury consumers in Asia.
The Missoni brand was born in 1953 at a workshop in Gallarte, Italy, when Ottavio Missoni and his wife, Rosita, began creating knitwear.
Known for the trademark Missoni zig-zag pattern, the brand has become a favorite of fashionistas, including Kate Moss and Kate Middleton.
The Missonis used their flair for design and business savvy to move beyond knitwear, starting a hotel chain and a line of housewares.
In 2011, the fashion house partnered with Target to create a low cost, 400-piece line, including a bicycle that sported the trademark Missoni zig-zag.
Annuals sales of the Milan-based company are estimated to be between $75 million and $100 million.
ABC News' Alyssa Newcomb contributed to this report.