Firefighters have contained the blaze that destroyed part of a massive clock factory in northern Illinois, but officials say it may be a week before it is extinguished.

Police Chief Doug Bernabei says the fire that broke out around midnight on New Year's Eve at the Westclox complex in Peru is smoldering and then will erupt in flames. Bernabei says the city's fire department and departments from 15 other communities had started battling the fire with aerial trucks on Monday.

He says there is no danger of the fire spreading from the middle building to other buildings in the complex.

The last of area residents evacuated from their homes were allowed to return Monday morning.

Two teenagers were arrested charged with aggravated arson. Bernabei says there are no other suspects.