A “serious act of sabotage” disrupted Spain’s high-speed rail lines, the country’s transport minister said on Sunday, affecting thousands of travelers as transit operators worked to restore normal service.

The disruption was caused by thefts of cable parts on the line between Madrid and Seville, said Oscar Puente, the transport minister. “These incidents are very serious,” he said in a social media post, adding that the Spanish national police force was investigating.

Train service in Spain was being restored on Monday morning. Credit…Manu Fernandez/Associated Press

The cable thefts were not the only reason for the widespread disruptions, which affected more than 10,000 passengers, Álvaro Fernández Heredia, the president of Renfe, Spain’s national rail company, wrote in a post on X.

He also blamed a technical issue: After the thefts, a train also “snagged, dragging the overhead power line,” he wrote in Spanish.

It is the latest major disruption for Spain, which is still reeling from an unexplained electricity outage last week.

By Monday morning, Mr. Puente said in a post on X that high-speed rail service had been restored to 70 percent of its normal service, and that it should be back to normal by the afternoon.

This is a developing story. Check back for updates.