Five barges broke loose after two tow boats collided on the Mississippi River on Thursday afternoon, with one loaded with hazardous caustic soda overturned, officials said.

The towing vessels American Heritage and David G. Schert collided near Vacherie on the west and Gramercy on the east within the jurisdiction of St. John the Baptist Parish, officials said.

The overturned barge is out of the navigable waterway on the right descending bank, while the others were safely recovered, the Coast Guard said in a news release issued shortly before 10 p.m. Thursday.

The overturned barge released an unknown amount of caustic soda solution into the river, possibly as much as 23,672 gallons, the Coast Guard said. The material was expected to dissipate and neutralize soon after entering the water, posing minimal risk.

Nevertheless, St. James Parish Sheriff Willy Martin Jr. said deputies have told municipalities with drinking water intakes on the river to monitor water from the river in case the caustic soda has made it downstream.

Martin said anything that spilled from the barges is not expected to affect the Gramercy intakes, but authorities have notified St. John the Baptist because that parish also takes drinking water from the river.

The five barges broke loose about 2:30 p.m. about a half-mile upstream of the Veterans Memorial Bridge.

Deputies said the four-lane bridge was shut for about an hour and a half Thursday afternoon as a precaution. Martin reported about 4:30 p.m. that the bridge was fully reopened.

Petty Officer 2nd Class Jonathan Lally, a Coast Guard spokesman, said earlier Thursday a 2-mile stretch of the Mississippi between milepost 148 and 150 was a restricted zone for marine traffic, keeping deep draft vessels from going through.

Follow David J. Mitchell on Twitter, @NewsieDave.