HOUSTON -

Four separate crashes wreaked havoc for drivers on the North Freeway.

According to officials, the accidents backed up I-45 for several hours overnight Friday.

There were four accidents in total, two of which were connected.

The first happened on the North Freeway and Northville just after 10 Friday night.

For unknown reasons, a car slammed into a light pole on the side of the freeway.

When the Houston Fire Department arrived they blocked two right lanes.

Two men were taken to the hospital in serious but stable condition.

While the ambulance was sitting in the blocked lanes with its lights on, another driver slammed into the back of it.

The driver claims to not have seen the ambulance.

There was no one inside the ambulance at the time and no one was injured in that crash.

Approximately an hour and a half later, a police officer  was also involved in a accident.

The officer was traveling south on I-45 near North Shepherd, when police say a car suddenly veered into his lane, cutting him off.

In an attempt not to hit the car, the officer slammed on his breaks and crashed into a concrete wall.

The officer wasn’t injured, and the driver who caused the wreck kept driving.

Then around midnight a man driving an 18-wheeler southbound on the North Freeway, managed to escape after the truck erupted in flames.

The driver plowed into barrels and a concrete barrier while trying to enter an HOV lane.

The driver claims to not have seen the barriers, causing the truck to skid across the freeway and catching the cab of the rig on fire.

All four wrecks closed several main lanes, which were reopened by Saturday morning.