Traffic at the mouth of the Mississippi River was stopped Friday morning in advance of the storm.
The Army Corps of Engineers said it was closing a structure intended to keep storm surge out of the Inner Harbor Navigation Canal in Louisiana — known locally as the Industrial Canal — where levee breaches during Hurricane Katrina led to catastrophic flooding in 2005.
Mayor David Camardelle of Grand Isle, La., an inhabited barrier island and tourist town about 60 miles south of New Orleans, called for voluntary evacuations as he declared an emergency Thursday afternoon.
Louisiana officials were taking precautions while noting that forecasts show the storm veering to the east. The storm track had it likely brushing the southeastern tip of the state before heading toward the Alabama-Florida coast. And it was moving faster than last year's Hurricane Isaac, a weak storm that stalled over the area and caused widespread flooding.
"It should make that fork right and move out very, very quickly," said Jerry Sneed, head of New Orleans' emergency preparedness office.
Offshore, at least two oil companies said they were evacuating non-essential personnel and securing rigs and platforms.
In Washington, the White House said the Federal Emergency Management Agency was recalling some workers furloughed due to the government shutdown to prepare for the storm.
White House spokesman Jay Carney said President Barack Obama was being updated about the storm. He said Obama directed his team to ensure staffing and resources are available to respond to the storm.
Hundreds of thousands of federal workers have been furloughed under the partial government shutdown. It's unclear how many FEMA workers are being brought back.
In Mexico's Caribbean coast state of Quintana, the brief passage of Karen before the storm moved north caused authorities to close seaports and some schools, but little rain was actually reported.