BERLIN (CNN) -- Bomb squads in Germany successfully defused on Sunday two bombs and disposed of an additional air-dropped military device that had caused an evacuation of historic proportions in a city in the country's west.

The 45,000 evacuated residents of the city of Koblenz, situated on the Rhine and Moselle Rivers, were allowed to return home.

Workers rendered inert the two bombs, one 4,000-pound "air mine" and a smaller high-density explosive bomb. Then they destroyed a third non-explosive device by way of a controlled detonation, according to the Koblenz fire department.

The fire brigade had pre-warned the population about the controlled detonation to allay possible fears that one of the powerful bombs may have exploded.

Life had come to a standstill in the western German city of Koblenz, where 45,000 people -- nearly half of the city´s population -- had been evacuated after the discovery of several dangerous World War II bombs.

"It's the largest German evacuation since the end of the war," fire brigade spokesman Ronald Eppelsheim said Sunday.

For 65 years, the Rhine River hid two bombs and an fog-producing device that were dropped by American and British warplanes in the last years of the war. When water levels dropped to record lows last week, the bombs were finally found.

The function of the fog-producing device was to block the vision of anti-aircraft personnel on the ground during WW II to make it harder for them to fire upon the allied planes carrying out the bombing mission.

"While time passed by, and Koblenz was rebuild(ing), the bombs got even more dangerous," bomb-disposal squad member Jurgen Wagner said Sunday.

The largest of the explosives is a 1.8 metric ton British air bomb that has the potential to destroy the city´s center, according to the fire brigade.

But the focus of attention wasn't on the largest bomb -- it was on the much smaller, 125-kilogram (275-pound) American high-explosive bomb. It was "transformed on impact of the earth" making it more difficult to deactivate the detonator, Wagner said.

Last week, hundreds of volunteers started evacuating two hospitals and seven homes for senior citizens. A prison and numerous hotels are also affected by the shutdown.

By mid-Sunday morning, authorities declared the center of Koblenz a "forbidden area." About 1,000 authorities were searching the town to make sure any left behind leave.

The fire brigade built a wall of more than 2,500 sandbags since the bombs were found in the river. Water pumps draining part of the river help ensure the two four-men teams can defuse the bombs precisely.

Eppelsheim said he is optimistic the operation will be successful.

"People in Koblenz are used to bomb findings," he said.

Despite the inconvenience for those evacuated, the situation could have been much worse.

"If we had found an even larger bomb, we would have been forced to evacuate all 100,000 citizens of Koblenz," Eppelsheim said.

The deactivation of bombs is a common practice in Germany. Last year, a bomb exploded in the German town Gottingen -- killing three members of a bomb-disposal squad.

During World War II, an estimated 257 British air bombs were dropped on Koblenz alone, according to the local fire brigade. It is not known how many of them did not explode and have been forgotten.

Bomb-disposal squads have only managed to deactivate three of them until now.