Railroad blockades by radical teachers in Mexico are testing leftist President Andres Manuel Lopez Obrador's commitment to nonviolence.

Since taking office Dec. 1, Lopez Obrador has promised to handle all protests with negotiation, not force.

But teachers in the western state of Michoacan set up protest camps on railways in January, demanding back pay.

The teachers got their pay and freed some rail lines last week, but on Friday again blocked a key line leading to the Pacific coast port of Lazaro Cardenas.

Lopez Obrador is so frustrated that he's asked the country's human rights commission to recommend some way of ending the stoppages.

Thousands of freight containers have been backed up during the 25-day blockade, and some grain shipments have spoiled.