The break was reported shortly before 4:30 a.m. on Wilshire Boulevard between Bixel Street and Lucas Avenue in the Westlake District.
As of 10:45 a.m., Wilshire Boulevard remained closed, as crews worked to fix the ruptured 8-inch main. Repairs were expected to be finished around 4 p.m.
The break caused a big mess, as water bubbled up from underground and rushed down the street. About 20 to 30 customers were affected.
The cause of the break remains unknown.