The flooding was reported around 1:32 a.m. at 4th Street, according to the California Highway Patrol's traffic log.
At one point, both sides of the freeway were completely closed, but the northbound lanes were reopened around 4 a.m. Video from the scene showed a large amount of water that overtook the freeway.
All southbound lanes remained closed for several hours, but at least two were reopened around 12:30 p.m. A third lane would remain closed until further notice.
The Los Angeles Department of Water and Power said the flooding stemmed from a break in an 8-inch water main. Water was shut at 3 a.m. and was expected to be restored some time Wednesday afternoon.
Boyle Avenue was also closed between 4th and 5th streets.