The father of missing U.S. airman Halex Hale told NBC News on Sunday that he doesn't buy Italian authorities' theory that his son was drunk and fell into a rain-swollen canal.

Hale, 24, an Air Force staff sergeant from Middletown, Ind., disappeared July 2 near Venice in northern Italy. Grigoletto Michele, the national police captain in charge of the search, told NBC News that investigators have called off the search until new information emerges.

Air Force Staff Sgt. Halex Hale. Aviano Air Base via AP

Hale, who is assigned to the 31st Fighter Wing at Aviano Air Base north of Venice, has been in the Air Force for six years and at Aviano since February 2015, his mother, Amy Hale, told The Star Press of Muncie, Ind.

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Michele said Hale was reported missing after he left a friend's house about 10 p.m. (4 p.m. ET) on July 2. He said more than 200 people — working with divers, helicopters and search dogs — had scrubbed an area of almost 4 square miles but had found no sign of Hale or his belongings.

"The most plausible theory for now is that he was inebriated with alcohol, left the house and fell into one of the nearby canals, which were swollen due to particularly stormy weather," Michele said Sunday.

But Hale's father, Lance Hale, told NBC News from the base that he doesn't accept that theory, saying a fellow airman had told him that his son left the party without his wallet, keys and mobile phone, "which is very strange."

"I walked the route that leads to the square from [the friend's] house today several times, and it just doesn't make sense," Lance Hale said. "There are hard shoulders, trees, houses all along the way. One can't just slip into the water — you really have to climb into something and jump into it, even if the canal was swollen, as they say."

Air Force Capt. Michael Hertzog wouldn't comment on Hale's cellphone, credit card or automobile use because the investigation is continuing. He told The Associated Press that there were no indications that Hale had any difficulties on base or off.