LAWRENCE, Mass. -- A train derailment that caused a chemical spill Thursday is making for a lengthy cleanup in Lawrence, where hazmat teams were still at the scene early Friday.

NewsCenter 5's Gail Huff reported that some roads near the Andover Street crossing were still closed as workers removed sodium chlorate chemicals from the damaged tanker.

Trains are running again, however, though with speed restrictions that are causing delays.

The railroad tanker car derailed about 5 p.m. Thursday when a wheel malfunctioned, causing the tanker to collide with another freight car. The collision ripped open the side of the tanker.

That sent 400 pounds of the white chemical, commonly used to manufacture paper pulp and as an herbicide, pouring out of the tanker. It is not considered dangerous unless mixed with water.

About a dozen homes near the site were evacuated as a precaution. The order was lifted by Friday morning, and they were allowed to return home, but nearby St. Patrick's School was closed for the day.