Tens of thousands of residents in the western Texas city of Odessa were with little to no water service Tuesday due to a massive water main break.

The break occurred at around 6 p.m. local time Monday at the intersection of 42nd and San Jacinto streets.

Crews were unable to isolate the source of the break, forcing them to take the city’s water treatment plant offline, Odessa Mayor Javier Joven said at a Tuesday afternoon news conference.

“Because of the critical nature of the loss in pressure, we were compelled to take the plant offline, to begin the repairs that are ongoing as we speak,” Joven said.

According to the office of Texas Gov. Gregg Abbot, about 165,000 area residents were affected by the water outage, which prompted a disaster declaration for the area. Cases of water were being distributed to residents at several locations throughout the city. A boil water notice was also in effect.

Odessa Public Works and Utilities director Thomas Kerr said repairs were expected to be complete sometime Tuesday evening, after which the water treatment plant would have to be restarted.

“We will need to restart the plant, and start loading the pipeline system, getting people back in water,” Kerr said, adding it was a process that could take another 10 to 12 hours.

There was no immediate word on a cause, although the broken pipe was close to 60-years-old, Kerr said. 

Meanwhile, like much of the state, Odessa is seeing above-average temperatures for this time of year. On Tuesday, temperatures reached 100 degrees Fahrenheit, according to the National Weather Service

The agency warned people against working or playing outside for extended periods of time, and encouraged residents to stay hydrated and cool.

Odessa is also currently experiencing a “severe drought,” the weather agency said, and severe thunderstorms with lightning, hail and gusty winds are expected Tuesday night.