The number of children in Indonesia who have been diagnosed with polio has risen from 16 to 20.

The World Health Organization confirmed the additional cases in West Java province Tuesday.

A massive campaign was launched last week to vaccinate at least 6.4 million children.

Health officials believe a migrant worker or a Muslim pilgrim returning from Mecca in Saudi Arabia brought the polio virus into Indonesia, triggering the outbreak - the first in a decade.

Indonesia is the 16th country where polio has reappeared since 2003, and the first outside Africa and the Middle East. The outbreak has been traced to northern Nigeria, where hard-line Muslims had boycotted a vaccination campaign.

Some information for this report provided by AP and AFP.