London (AP) British Army engineers are trying to defuse a giant World War II-era bomb discovered in east London.

The 2,200-pound bomb was found Monday as construction workers
Began preparing a site for the 2012 Olympic Games.

A military spokesman says the work to defuse it is not going as quickly as hoped, but no details of the difficulty are being offered. He says the bomb started to tick at one point but engineers dealt with that problem.

Service on two nearby subway lines has been suspended as a precaution.

Police say the bomb is the largest found in London in three decades.

Thousands of bombs fell on east London during World War II and unexploded devices are found from time to time, particularly at construction sites. Bombs as large as two tons were dropped on the city during the war, but an unexploded bomb of the size of the one
found Monday is very rare.