LYONS, Colo. (AP) - Gerald Guntle dials his sister's home multiple times a day, desperate to find out if she survived the widespread flooding that shattered the Rocky Mountain foothill town of Lyons, but the phone just rings and rings.
"If there was no phone service, I wouldn't expect to keep getting ringing. That's what has me scared," said the Tucson, Ariz., man, whose sister is among hundreds of people listed as missing in a disaster that is already believed to have killed as many as eight people.
Officials hope the number of missing will drop rapidly as communications are restored and people are evacuated throughout the region, as it did in Larimer and Boulder counties, where some 487 people dropped off missing-persons list over the weekend.
But faced with a lack of information, friends and relatives are struggling to avoid thoughts of worst-case scenarios.
In Estes Park, a tourist haven that serves as a first stop for many people entering Rocky Mountain National Park, Tony Bielat was searching for information about an elderly man who lives alone in nearby Glen Haven, where cabins and boulders washed down a swollen river.
"The problem is no one knows who has been rescued," Bielat said.
Officials were wading through the rubble in Glen Canyon on Monday, checking every structure in the town one by one.
Precise accounting of the missing remains elusive, with state and county agencies sometimes reporting conflicting totals. Colorado officials listed 1,253 people missing statewide at one point Monday and then updated it to just 658 later in the afternoon.
Most of the missing were in Larimer and Boulder counties, which lie north of Denver and are dotted with self-reliant mountain hamlets where privacy-conscious residents live in remote homes difficult to access even in ideal conditions.
Boulder County has assigned 10 police detectives to search for the missing. Officials are struggling to gauge how many people might actually be in danger as they field hundreds of calls from relatives, friends, estranged siblings and also near-strangers.
Rescuers and shelter workers are taking down lists of evacuees to feed to county officials, and people are asked to call in when they locate their relatives. Federal officials Monday repeatedly implored people affected by the flooding to call and reassure their loved ones.
In the funky mountain town of Lyons, stranded residents were unsure how to communicate their status. Telephone landlines were knocked out as floodwater rushed in Wednesday, and most people's cellphones died long ago.
One man drove with his young son past the shuttered shops on a muddy and abandoned Main Street searching for guidance.
"Do you need something?" shouted Glenn Scott, who was walking his two golden retrievers. It's become the town's new greeting.
The man said he was looking for Federal Emergency Management Agency headquarters to let officials know the pair was OK so they wouldn't be listed among the missing.
But the only official seen around town that day was a local emergency worker telling residents it was their last chance to evacuate.
Guntle is hoping his sister and her two children- his only family now that his parents have passed away- are among the holdouts who have chosen boiled water, pantry items and isolation over homelessness.
He called the makeshift shelter for displaced Lyons residents on Friday and was told his sister hadn't come in. He called 10 more times that day, but couldn't get through again.
"I wish they had a list of people who are OK," he said.
A Red Cross website where evacuees can register to let people know they're safe had more than 960 people registered by Monday.
Some mountain residents, however, criticized the list, saying a website was the last thing on their minds after days of precarious existence and evacuation by zip-line, helicopter or military truck.
Families and friends are likely to suffer from acute stress as they wait, and should have access to emergency psychological first aid through FEMA, said Robyn Gershon, a professor at the University of California, San Francisco, who researches disasters.
"The toll on both the person whose missing- knowing that their families are worried_ and the family and friends waiting to hear is horrific," she said, adding, "Every minute will seem like a day."
Some stranded residents are going to great lengths to reassure their loved ones. Gondalo Orejel's childhood friend and roommate hiked to a satellite phone in a mountain quarry on Saturday to let him know he was safe.
"It was the first time I smiled since it happened," said Orejel, who lives in Lyons but was visiting Boulder when the flood struck.
Associated Press writers Jeri Clausing in Estes Park and Dan Elliott in Denver contributed to this report.
Hannah Dreier can be reached at http://twitter.com/hannahdreier
(Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)