(Reuters) - Commercial shipping traffic on the Mississippi River north of St. Louis was halted on Tuesday after a vessel collided with a gate at Lock 27 near Granite City, Illinois, the system's busiest lock, a U.S. Army Corps of Engineers spokesperson said.
The accident occurred in the lock's auxiliary chamber, which had been the only operational lock as the main chamber is closed for scheduled repairs until March.
Corps personnel were assessing damages and could not immediately estimate how long the lock would remain out of service.
Nine upriver vessels and five downriver vessels were waiting to pass through the lock as of 12:45 p.m. CST, according to the Corps' Lock Performance Monitoring System website.
Although vessel traffic on what is known as the mid-Mississippi River was seasonally slow, the lock closure was the latest logistics headache for shippers that rely on the inland waterways system to haul billions of dollars of grain, coal, fertilizer and other commodities.
Low water along a busy stretch between St. Louis and Cairo, Illinois, has been threatening to disrupt traffic on the drought-drained river since December.
Dredging operations have slowed traffic at various points of the river for months.
A six-mile stretch at Thebes, Illinois, has been closed for 16 hours a day since December as the Army Corps works to remove river-bottom rock pinnacles that pose a threat to boats during low water conditions.
(Reporting by Karl Plume in Chicago; Editing by Gerald E. McCormick and Bob Burgdorfer)