A lock gate fell off Markland Locks and Dam Sunday morning, causing the Ohio River to be closed to commercial boat traffic for about 11 hours until an auxiliary lock could be placed in operation, according to news accounts in Louisville and Cincinnati.

The equipment failure is major, the Army Corps of Engineers was quoted as saying.

Sonar is to be used today to find the gate that fell, the Louisville Courier-Journal reported.

A trip through the locks takes longer when the smaller auxiliary lock is used, the news reports said.

About 15 barges or ships use the locks on an average day, and in the course of a year 55 million tons of cargo are carried through. That's equivalent to the amount of cargo 10,000 semis could haul. Coal is the most common cargo.

The Corps of Engineers said it did not know how long the lock would be closed for repairs. A major overhaul project paid for with federal stimulus money is scheduled to be done next year.

The lock is 1,200 feet long and 110 feet wide. The auxiliary lock is 60 feet wide. Barges and boats traveling on the river enter the lock, where the gates close behind them and the water level is raised or lowered, whichever is needed to get them to the elevation they need. When the gates malfunctioned Sunday, water flow could not be controlled.

Cincinnati television station WCPO had reported Sept. 19 that Markland Locks would be closed the following two weeks for inspection. An update was not available.