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Tarvaris Jackson lost control of his car while doing 70 in a 30 MPH zone -- slamming into a signpost and crashing into a ditch, this according to the police report obtained by TMZ Sports.

The former NFL quarterback was fatally injured in the April 12 crash in Montgomery, Alabama around 8:50 PM.

According to the police report, the road where Jackson crashed was not well lit -- and he lost control while going around a bend.

When emergency personnel arrived at the scene just a few minutes after the crash, Jackson was "unable to give a reason why he crashed his vehicle."

The 36-year-old was transported to a nearby hospital where he was later pronounced dead.

The report also says Jackson was not tested for alcohol or drugs at the scene.

Officials also note Jackson WAS wearing his full shoulder and lap seatbelt at the time of the crash.

It was also noted the roadway way dry and the conditions outside of the poor lighting were normal.

They seem to blame the crash on Tarvaris driving at a "high rated speed."

Jackson was laid to rest of over the weekend -- but due to the COVID-19 pandemic, mourners inside the church were limited to groups of 10 or less.