By Alex Dobuzinskis

LOS ANGELES (Reuters) - Drivers in Los Angeles saw limited congestion on Saturday near a key freeway corridor shut down this weekend in what has been dubbed "Carmageddon 2," due to fears of gridlock from a 53-hour construction project, officials said.

A 10-mile (16-km) stretch of the 405 Freeway at the Sepulveda Pass, normally the nation's busiest thoroughfare, was closed at midnight on Friday for a $1 billion freeway widening project.

But so far, despite slowing near the project itself, traffic seemed to be zipping along in the city as a whole, said California Highway Patrol spokeswoman Officer Charmaine Fajardo.

"So far so good, it looks like people are heeding the information we've put out there and staying out of the area," Fajardo said.

Construction crews with giant cranes on Saturday chipped away at a bridge spanning the 405 Freeway in the city, with pieces of concrete dropping dozens of feet (meters) to the ground below. A four-foot (1.2-metre) pad of dirt laid down in advance protected the pavement from the falling debris.

The work is to widen the bridge itself to expand the freeway below.

The project comes just over a year after a similar weekend construction project shut down the same area in what was dubbed "Carmageddon," in anticipation of massive congestion that never came to pass as many drivers stayed home.

This year, the project has caused some anxiety nonetheless among officials and motorists in the city where car travel is king but only very limited congestion had materialized.

Workers did experience a brief hiccup during the demolition early Saturday evening, when a large section of the Mulholland Bridge fell down, officials said. They noted that another larger-than-usual chunk had fallen during the morning.

"This is not cause for concern," officials said in a statement. "It did not damage the newly constructed portion of the bridge nor should it cause any delays."

The shutdown of the 405 Freeway along the Sepulveda Pass is scheduled to end at 5 a.m. on Monday, said Marc Littman, a spokesman for the Metropolitan Transportation Authority.

The construction crew on the project stands to be fined $6,000 per closed lane for every 10 minutes that the project extends past its scheduled ending on Monday morning, officials said.

(Reporting by Alex Dobuzinskis; Additional reporting by Mary Slosson; Editing by Colleen Jenkins and Todd Eastham)