By Tom Bassing

BIRMINGHAM, Alabama (Reuters) - Authorities have doubled the reward to $30,000 for information leading to the capture of a man suspected of fatally shooting three men near Auburn University in Alabama after an overnight raid in Montgomery targeted a residence with nobody home.

Police and federal authorities on Monday night fired tear gas into a home that "turned out not to be correct," FBI spokesman Douglas Astralaga said on Tuesday, leading them to renew their manhunt for Desmonte Leonard, 22.

Leonard, wanted on three state warrants for capital murder, is the prime suspect in Saturday's shooting in which two former Auburn University football players were killed and a current player was wounded.

Three men were killed and three wounded in the shooting at a pool party at an apartment complex near the Auburn campus. One man remains in critical condition with a bullet wound to the head.

The original reward fund of $15,000 came from a $10,000 contribution by the FBI and $5,000 from the U.S. Marshals Service. The University of Auburn has pledged a further $10,000 and the city of Montgomery $5,000 to the reward fund, Auburn city spokesman David Dorton said on Tuesday.

Police said they believe Leonard fled to Montgomery, about 60 miles from Auburn, and said they would continue their search there.

"We're going to continue to push forward with the search," Astralaga said.

During the raid that began Monday and ended in the early morning hours on Tuesday, authorities thought they heard coughing coming from inside, according to local media reports.

Asked about the reports of coughing, Astralaga said, "There are high-level stresses when you're going after an individual as dangerous as this one."

Police also believed they had located the suspect in the attic using thermal imaging, but "obviously it's not 100 percent reliable," Astralaga added.

Two of the men killed Saturday night - Edward Christian and Ladarious Phillips, both 20 - were former members of the Auburn football team. Current Auburn player Eric Mack, 20, also was wounded in the shootings.

Another victim, 20-year-old John Robertson, remained hospitalized and was said to be clinging to life after suffering a gunshot wound to the head.

Two other men, Gabriel Thomas, 41, and Jeremy Thomas, 18, have been charged with hindering prosecution in the case. Police said the two Montgomery men provided false information to law enforcement officers searching for Leonard.

(Editing by Daniel Trotta and Will Dunham)