EL PASO, Texas (AP) — More than 100,000 residents in the Texas border city of El Paso were left with little to no water after a main break over the weekend, and it was expected to take till midweek for operations to return to normal, officials said.

The break in the 36-inch water main line happened late Saturday night in El Paso, which has a population of about 700,000, officials said. Gilbert Trejo, an official with El Paso Water, called it “an event of unprecedented proportion.” He said the break was made even more impactful because of “the way the pipeline itself was designed along with how different connections of smaller lines were made to it.”

A boil water notice was issued, and water distribution centers were set up, officials said.

Classes were canceled Monday at more than a dozen schools in the El Paso Independent School District due to the outage. Other schools in the area remained open but were under the boil water notice.

Trejo said that about 38,000 customer connections were put out of service because of the break, which translates to over 100,000 residents impacted. He said that more than 15 water reservoirs “essentially drained out.”

He said there isn’t enough information yet to determine what caused the break.

Trejo asked for patience as they make repairs and go through the process to get the water flowing again.