MEXICO CITY (AP) –  Mexico City officials say intentional sabotage may be contributing to recurrent water shortages that have caused protests on the streets of the city of 9 million people.

In recent weeks, officials have blamed dry faucets in many neighborhoods on everything from power shortages to failing pipes and the spring dry season.

But on Wednesday, Mayor Miguel Angel Mancera said some group has been shutting off water distribution valves at about 50 points in the sprawling megalopolis. Mancera did not say who was believed to be responsible, but said anyone caught closing valves would be arrested.

The mayor says the city is purchasing lockable covers for the valves.

Residents will vote for Mexico’s president and the city’s mayor in July 1 elections, and some fear the sabotage may be politically motivated.