Jackson is reduced to one lane between Clinton and Canal, and traffic is getting by on Clinton in just one lane from Adams to Jackson.
The phone company will work through Wednesday night to secure the structure and ensure that phone lines are unaffected by repairs.
On Tuesday night, the 13-inch water main ruptured under the street. By morning, crews made temporary repairs to the street, which had buckled.
There's no estimate yet on how long it will take for the repairs to be completed.
"We'll just have to dig and see what repairs we'll have to make as quickly as possible," water department spokesman Tom LaPorte said.
Early reports indicated an Amtrak parking garage experienced some flooding, LaPorte said.
"Water was coming up to the bottom rims of cars," he said. "It was a significant amount of water, apparently."
LaPorte said the broken main did not affect water service for nearby residents.