Dozens of people were reportedly injured in a commuter train crash near Oxnard, Calif., during Tuesday morning's rush hour. Emergency crews swarmed the area, where several Metrolink train cars were thrown onto their sides by the powerful collision.

The crash occurred around 5:40 a.m. local time in Ventura County close to Oxnard, some 70 miles northwest of downtown Los Angeles. Reports of casualties vary. At least 30 people were injured; 28 were sent to the hospital.

Owing to extensive damage, officials aren't yet sure what type of vehicle it was that was struck at the road-level crossing; it was first reported to be a large truck and may have been a farm vehicle.

Dramatic images from the scene show a large fire burning in the early-morning darkness. According to the most recent reports, the vehicle may have already been burning as it sat on the track.

Details are still emerging from the scene; we'll update this post with more news.

Update at 12:40 p.m. ET: Engineer Said To Have Braked

The Los Angeles Times reports, "Fire officials at the scene said the train was traveling at its cruising speed of 79 mph when the conductor spotted the flaming truck and anticipated the crash from 'a far distance out.' "

Update at 12:30 p.m. ET: 28 People Sent To Hospitals

Ventura County Fire Department officials say 28 people have been sent to hospitals, with four of them in critical condition," member station KPCC reports. The station adds that 23 other people were not injured.

The Federal Railroad Administration is sending investigators to the scene. An agency spokesman says, "We will establish what lapses, if any, occurred and order any necessary corrective actions."

Our original post continues:

From CBS Los Angeles:

" 'For some reason there was a tractor trailer on the tracks there at Rice Avenue and Train 102 collided with it,' said Scott Johnson of Metrolink."The truck caught fire and four train cars derailed. The driver of the truck fled the scene, but was later arrested, the VCFD said."

Fire officials say the train was in "push mode" — with its locomotive in the rear — when it struck the truck. The locomotive was the only part of the train to remain firmly on the track; skid marks from the passenger cars show that they slid away from the engine.

Trains in push mode are controlled by an engineer who sits in a cab in the leading passenger car. Its merits and safety have been a subject of debate — including in a lawsuit against Metrolink that was sparked by a fatal accident back in 2005.

In 2006, the Federal Railroad Administration issued a report that found "there is little difference in safety between passenger trains pushed by locomotives and those that are pulled," the Los Angeles Times reported at the time. "Researchers noted, however, that more people have died in accidents involving pushed trains."

In online documents, the rail service says it has long employed the push-pull practice according to U.S. safety regulations:

"Since Metrolink began service in 1992, we have operated our trains using the push-pull configuration. When the locomotive is in the rear, the engineer sits in a control cab in the front of the lead passenger car (called a cab car) to control the train. A cab car contains a cabin where you will find all of the same controls found in a locomotive."Push-pull was developed for worldwide use as an appropriate alternative to locomotive-only operations. It has proven to be very safe, and is now used by virtually all commuter railroads in North America. Federal standards establish the specifications for cab or lead passenger cars, and Metrolink's fleet complies with all applicable regulations."

Update at 8:43 p.m. ET: Suspected arrested

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