A nurse who stopped to help the victims of a serious crash in Maryland early Wednesday was hurt after she plunged more than 75 feet into a river, officials said.

The woman fell into the Monocacy River in Frederick County after she tried to cross from the eastbound lanes to the westbound lanes of a bridge and apparently was unaware there is no median between the lanes, Maryland State Police said in a statement.

The woman, a 47-year-old trauma nurse, and her husband were traveling eastbound on I-70 about 4:45 a.m. when they saw that a semitractor-trailer and dump truck had crashed on the westbound lanes of the bridge, police said.

The semitractor-trailer, which was loaded with asphalt, slammed into the back of the dump truck, which was loaded with concrete.

The semitractor-trailer hit the right concrete wall of the bridge, jackknifed and caught fire. The dump truck crashed onto its side and spilled some of its load of concrete onto the bridge, dramatic photos taken from Chopper4 show.

The good Samaritan ran to help the two drivers and plunged into the river.

Her husband called for help immediately, and a trooper pulled her to shore.

Chopper4 flew over the scene as rescue crews secured the woman to a gurney.

The nurse and the dump truck driver, a 53-year-old Baltimore man, were rushed to University of Maryland Shock Trauma Center by helicopter. The semitractor-trailer driver, a 58-year-old man from Sparrows Point, Maryland, was taken to Meritus Medical Center.

Before the crash, a motorist reported that a commercial truck driver was traveling westbound without the truck's lights on. The crash occurred moments later, as troopers tried to find that truck.

The interstate was closed in the aftermath of the crash.