( CNN ) -- Oil companies evacuated workers from offshore wells , New Orleans prepared for possible flooding and Louisiana Gov . Bobby Jindal declared a state of emergency as a tropical depression formed Thursday in the Gulf of Mexico . The National Hurricance Center issued a tropical storm warning Thursday evening for an area stretching from Pascagoula , Mississippi , to Sabine Pass , Texas . The hurricane center said tropical storm conditions are expected somewhere within the warning area . New Orleans -- much of which sits below sea level -- is likely to see 8 to 10 inches of rain in the next few days , Mayor Mitch Landrieu told reporters . `` What we do know is there 's high wind , there is a lot of rain and it 's going slow , '' Landrieu said . `` That 's not a good prescription for the city of New Orleans should it come this way . '' It was six years ago this week that Hurricane Katrina slammed into the Gulf Coast , devastating coastal Louisiana and Mississippi and inundating much of New Orleans . Landrieu urged residents to start collecting the items they might need in case of flooding or a hurricane , such as bottled water , batteries , nonperishable food , first-aid kits and family documents . They may not be needed this time , he said , `` But we seem to be entering the more active phase of the storm season . `` It is important for citizens to remember it is individual preparation at the end of the day that matters the most , '' he said . Firefighters had been battling a huge wildfire in a swamp on the city 's east side for several days as the blaze spread smoke over much of the city . Landrieu quipped that city officials had hoped for rain , `` and it appears as though our prayers have been answered . '' As of 7 p.m. Thursday , the tropical depression was centered about 225 miles south of the mouth of the Mississippi River and was moving northwesterly at about 6 mph . It had maximum sustained winds of 35 mph . In advance of the weather , BP and ExxonMobil ordered their Gulf rigs evacuated and have shut down their wells , spokesmen for those companies told CNN . Chevron , meanwhile , has ordered nonessential workers off the platforms , and Shell said it had begun taking some of its workers back to shore Thursday afternoon . `` Weather conditions are already impairing staff movement , but we are using all available resources to safely evacuate employees , '' Shell said in a written statement . `` The number of evacuated personnel will depend on weather conditions , and we will only transport personnel if safe to do so . '' `` Interests along the entire northern Gulf of Mexico coast should monitor the progress of this disturbance , '' they noted . In the state of emergency declaration , Jindal authorized the state Homeland Security and Emergency Preparedness director `` to undertake any activity authorized by law which he deems necessary and appropriate '' to prepare for the storm . CNN 's Dave Alsup and Vivian Kuo contributed to this report .
NEW : Storm warning stretches from Pascagoula , Texas , to New Orleans , Texas . New Orleans governor declares state of emergency . New Orleans mayor warns residents to prepare for flooding . ExxonMobil joins ExxonMobil and ExxonMobil in evacuating offshore platforms .