The Florida Department of Transportation announced Saturday that it is reopening the 14-mile stretch of Interstate 75 that was shut down due to rising river water under the highway. Officials said the Myakka River's water levels had receded enough to safely reopen the highway.

But, officials warned they may have to shut down the interstate again if water levels rise once more.

Officials had shut down I-75 from mile marker 179, near North Port and Toledo Blade Blvd. to mile marker 193, near Jacaranda Blvd, and long detours were in place.

I-75 is the main highway on the west coast of Florida and is a main route for travelers between Tampa-St. Petersburg and Fort Myers and Naples.

The Centers for Disease Control and Prevention put out a health advisory to healthcare professionals treating patients in areas affected by Hurricanes Fiona or Ian, telling them to maintain a high index of suspicion for carbon monoxide poisoning.

"Other people who may have been exposed to the same CO source may need to be identified and evaluated," the CDC said in a health advisory.

-ABC News' Eric Strauss

Four people have died in North Carolina since Friday in storm-related incidents, state officials said Saturday.

Two people died due to car accidents caused by storm conditions, one man drowned in his car and a fourth man died due to carbon monoxide poisoning from a generator.

Among those killed was a 25-year-old man who lost control of his vehicle and hydroplaned into another vehicle, a 24-year-old woman whose vehicle went off a wet road and struck a tree and a 22-year-old man who drowned when his truck left the roadway and submerged in a flooded swamp.

A 65-year-old man died Saturday from carbon monoxide poisoning from a generator running in his closed garage while the power was out. His wife was hospitalized.

“The storm has passed, but many hazards remain with downed trees, downed power lines and power outages,” said North Carolina Gov. Roy Cooper in a press release. “We mourn with the families of those who have died and urge everyone to be cautious while cleaning up to avoid more deaths or injuries.”

A flood watch remains in effect in parts of Virginia and West Virginia on Saturday as Ian’s remnants push north.

The storm is significantly weakened, but winds may still top 35 mph as rain covers the Mid-Atlantic and Northeast this weekend.

-ABC News’ Daniel Amarante

President Biden has declared that an emergency exists in North Carolina and ordered federal assistance to help with the state's response in the aftermath of Hurricane Ian.

"The President’s action authorizes the Department of Homeland Security, Federal Emergency Management Agency (FEMA), to coordinate all disaster relief efforts which have the purpose of alleviating the hardship and suffering caused by the emergency on the local population," the White House said in a statement released early Saturday.

FEMA is authorized to identify, mobilize and provide equipment and resources to help the recovery efforts on the ground.

"Deanne Criswell, Administrator, Federal Emergency Management Agency (FEMA), Department of Homeland Security, named John F. Boyle as the Federal Coordinating Officer for Federal recovery operations in the affected areas," said the White House."

Ian’s winds have come down to 50 mph as the storm continues to move north as a post-tropical cyclone.

Ian will continue to weaken as it moves north, and will bring heavy rainfall in short periods of time through the morning hours, prompting flood watches to be issued from North Carolina to West Virginia.