Residents in the Eldorado section of Altoona are under a boil water advisory following a water main break in the area early Monday.

The Altoona Water Authority said customers in Eldorado Springs, the Klock development and in some parts of southwest Altoona may experience contamination in their water supply or an interruption in service after the main break on the 800 block of 36th Street.

Affected residents should have received notification by phone from the authority announcing the advisory and a subsequent notice will be sent when testing is complete and the water is deemed safe.

Testing can take between 36 and 72 hours.