INDEPENDENCE, Ore. -- Polk County authorities have given up their search for two brothers who disappeared Sunday while fishing along the banks of the Willamette River.
Now they say they'll begin looking for bodies in the water.
Police and Polk County sheriff's deputies said there was no indication of foul play or that the boys had run away.
The two boys, 20-year-old Alvin Troub and his younger brother, Michael Runyon, an 8-year-old with autism, were last seen Sunday fishing on the Willamette River banks in Independence.
Mary Troub, the boys' mother, said Michael cannot swim and was probably "very, very scared."
On Sunday and Monday, search crews used boats, divers and cameras along with dogs, helicopters and volunteers to try and find the two boys. Investigators were focusing on the river, but family members were holding out hope that the boys did not fall into the surging water.
"I feel like they're out there. I feel like they're alive," Mary Troub told KGW on Monday. "They're extremely close. Alvin's like a role model to Michael. He loves him to death."
Authorities found the boys' fishing equipment yards away from the river, but no sign of them. The river was running very high, they said, and the boys could have fallen in.
"Our fear is that they're in the water," said Independence Police Department Chief Vernon Wells.
More than two dozen volunteers are searching the murky water and thick brush along the banks -- but say the odds of finding the boys alive are dwindling by the hour.
"The assumption is they somehow got in the river and most of our search is concentrating on the river," Wells said.
Troub isn't so sure.
"I'm kind of thinking at this point they were taken," she said.
"We just can't figure it out, [the boys' mom] was thinking someone may have taken the boys, but Alvin is such a big boy," said their aunt, Laurie Runyon. "Alvin takes really good care of his fishing poles. I don't know what's going on."
The boys' pictures are plastered on flyers in store-front windows from Independence all the way to Monmouth.
Police reiterated they were working "every possible angle" in the case, including the possibility the boys may have been abducted.
At least one boat will resume searching for the boys Tuesday should darkness and weather conditions force a suspension of the hunt Monday night.
KGW Reporters Mike Benner and Erica Heartquist contributed to this report.