SOUTH FULTON, Ga. -- Investigators now believe they know the cause of a fatal crash that happened Thursday afternoon on Camp Creek Parkway.

Fulton County Police Department said preliminary information reveals the bus was traveling east on Camp Creek Parkway and attempted to change lanes when it collided with a Chrysler already in that lane.

According to police, the bus driver steered to the left and lost control. That's when the bus entered the median, that was uneven, and rolled over. While upside down, the bus slid into oncoming traffic and on top of a Mercedes that was traveling westbound.

Photos | Fatal church bus crash

The bus was transporting a crew of high school students and chaperones from Mt. Zion Church in Huntsville, Al. to the airport for a mission trip to Africa. The crash killed one of the teenage passengers, Sarah Harmening. Dozens more remain in the hospital.

The driver of the Chrysler and the two occupants of the Mercedes were transported to the hospital as well. Fulton County Police said while others have critical injuries, none of them are believed to be life-threatening.

Police said Friday that it was believed that the bus driver remained hospitalized and had not been interviewed yet.

The investigation is ongoing and charges are pending. Speed was not believed to have been a factor in the crash, police said.

WHAT WE KNOW ABOUT THE VICTIMS

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Sarah Harmening was on a bus with many other teens and young adults on Thursday when the bus somehow overturned on Camp Creek Parkway. They were heading to Hartsfield-Jackson International Airport - and then Botswana - as part of a mission trip from Huntsville, Ala.

Hermening's parents shared her last journal entry that showed her love for Jesus Christ.

Atlanta Medical Center's South campus in East Point took in 15 patients. All of them are expected to be treated and released.

MORE COVERAGE: 1 killed, dozens injured after church bus overturns

Hospital officials said it was an emotional day for them as families kept pouring in wanting to know the status of their loved ones.

At Grady Memorial Hospital downtown, officials there said they are treating four patients who are now in stable condition. They received nine patients from the crash but treated and released five of them. Atlanta Medical Center has four patients being treated.