After a fruitless attempt to defuse a WWII-era bomb, residents of a Frankfurt neighborhood are to be evacuated for the second day running on Wednesday evening.

Bomb disposal experts will endeavour once again to defuse the undetonated 50-kilogram explosive - this time using a different tool.

Some 1,400 people who live within a 400-meter radius of the building site where the bomb in the Seckbach district was discovered must vacate their homes.

Experts also suspect that a second bomb could be buried directly beneath.

"We'll only know whether that's the case when the bomb is defused," said a fire rescue service spokesman on Wednesday afternoon.