The Latest: Crews working to keep I-55 south of St. Louis from shutting down amid floods

In this aerial photo, flood water covers Interstate 44, Wednesday, Dec 30, 2015, in Valley Park, Mo. A rare winter flood threatened nearly two dozen federal levees in Missouri and Illinois on Wednesday as rivers rose, prompting evacuations in several places. (AP Photo/Jeff Roberson) (The Associated Press)

People stand on a hill to get a better look at floodwater from the Bourbeuse River Tuesday, Dec. 29, 2015, in Union, Mo. Flooding across Missouri has forced the closure of hundreds of roads and threatened homes. (AP Photo/Jeff Roberson) (The Associated Press)

Volunteers form a human chain as they help load sandbags Tuesday, Dec. 29, 2015, in St. Louis. Flooding across Missouri has forced the closure of hundreds of roads and threatened homes. (AP Photo/Jeff Roberson) (The Associated Press)

The latest developments on flooding in the Midwest (all times local):

1:30 a.m.

Crews are trying to keep a major interstate highway south of St. Louis open amid historic flooding.

The Missouri Department of Transportation said Wednesday night that I-55 at the Meramec River near Arnold could close overnight or Thursday.

An aggressive sandbagging operation was underway to keep the highway from closing. Other connections between St. Louis and Jefferson counties already are closed, including I-44 over the river.

Local media report the traffic has been rerouted. But a spokeswoman for the Department of Transportation told the St. Louis Post-Dispatch (http://bit.ly/1YTOKkk ) the detours are temporary to move in more equipment for flood-fighting.

Marie Elliott says, "The goal is to keep the highway open."