GAINESVILLE, Ga. (AP) _ Two workmen died and two others were in critical condition Wednesday after apparently breathing a deadly gas while working in a septic tank.

Authorities identified the dead men as David Hammond, 27, of Oakwood and Eugene Talmadge Kidd, 53, of Gainesville.

Listed in critical condition at Northeast Georgia Medical Center were David Hammond's brother, Danny Hammond, 29, of Gainesville and another worker, whose name was not released because his family had not been notified.

All four were employees of Hammond Septic Tank Service in Gainesville. Billy Hammond, who owns the company, is the father of the Hammond brothers.

The men were working in a septic tank next to the Con Agra Supply Co. on U.S. 129 south of Gainesville when they lost consciousness and collapsed, said Hall County firefighter Todd Orr.

Orr said he and another fireman, Jimmy Wilson, put on gas masks and climbed through the three-foot-square hole in the ground that led into the septic tank.

''One of them was groaning when I got down in there,'' Wilson said. ''Two of them had their heads in the water.''

Orr and Wilson fastened rescue belts around each of the unconscious men, and firemen above lifted the men from the 15-foot-deep tank.

''Right now, what we think what happened was there was a large buildup of gas, probably methane gas,'' said Jim Lancaster, a fire department battalion chief. ''Methane gas is odorless and colorless, so they wouldn't know it was in there. It just displaced the oxygen.''