The 48-inch water pipe burst at 9 p.m. Sunday evening near Rockville Regional Park, releasing 100 million tons of water into close-by Rock Creek.
Following the main water break, Montgomery County ordered 1,200 restaurants that use water from the Washington Suburban Sanitation Commission to close on Monday, according to NBC4.com.
The commission lowered the number of closed restaurants to 700 on Tuesday, according to The Washington Post.
The commission ordered residents in the Shady Grove, Germantown, Olney, Hampshire Green and Burtonsville areas of the county to boil water and restrict their water usage for at least three days, according to NBC4.com.
Utility workers say residents with low water pressure and/or little water are subject to water contamination. The closing affected food services facilities, including fast-food restaurants, in northern Montgomery County, according to NBC4.com.
Thousands of customers faced low water pressure or had no water, according to the Post. Residents of Poolesville and Rockville are not affected by the water contamination, NBC4.com reported.
A second system break occurred around 8 a.m. Monday near Redland Road, southeast of Gaithersburg, which was likely due to pressure built up from valves shut off during the previous break. Only 81 customers were affected, according to The Post.