SILT, Colo. — Dee Hoffmeister awoke at 3 a.m. one night in early March with her head spinning. The oversize red numbers on the alarm clock were a blur. She couldn't get out of bed without her husband's help.

It was a familiar feeling.

A gas well a stone's throw from the Hoffmeisters' retirement home south of Silt on Colorado's Western Slope was on fire and the area was filled with oily smoke. Hoffmeister, 69, who has suffered intermittent mysterious ailments since that well was drilled in 2005, ended up at the emergency room.

Hoffmeister, and hundreds of others, believe their aches and pains — and more serious ailments — are directly related to some of the 31,522 wells that dot vast stretches of the Piceance Basin where they live and other oil-rich areas of Colorado.

So do some doctors who treat them. But in this state and others, there are no studies proving a connection. And no agency has been charged with documenting all health concerns, leaving sick residents in limbo.

Some energy companies have been willing to help — without acknowledging a connection between illnesses and wells.

Bill Barrett Corp., an oil and gas exploration company, offered to pay for Hoffmeister to stay in a motel or apartment for six months. It also added controls to minimize emissions. Hoffmeister's condition improved.

"We're trying to be as responsive to issues that people perceive as we can," said Jim Felton, a manager with Bill Barrett. He said the company spends several thousand dollars per well to lessen emissions near homes.

But industry representatives generally downplay residents' tales of vertigo, bloody noses, tumors, burning lungs and aching joints as well as the more exotic illnesses — rare adrenal tumors, nerve damage and a neurological condition that makes sufferers speak in foreign accents.

Chemicals like toluene and benzene, two of many toxins used and released in the drilling process, are known to be toxic in high concentrations, but there is no proof that long-term exposure to low levels is harmful.

Even more problematic, energy companies are not required to reveal which chemicals they use because it is considered proprietary information. Therefore, it's impossible to positively connect symptoms and illnesses.

Dr. Kendall Gerdes, a Denver physician who specializes in internal and environmental medicine, said little medical data exist on the effects of certain chemicals or mixes of chemicals on vulnerable individuals. There also is little proof that certain chemicals cause certain illnesses, and that makes physicians reluctant to link the two.