CHICAGO (CBS) — The Chicago Police Department said investigators will be looking at dash-cam video from a department SUV to determine what led two officers to be injured when they drove into a construction site early Thursday morning.

Two Chicago police officers were seriously injured when their squad car crashed into a road construction site in the Avalon Park neighborhood.

Police said the officers were on duty in a marked patrol SUV around 4:20 a.m. when they crashed through a construction barrier near 83rd and Woodlawn. The vehicle fell into a hole in the construction site.

Police Superintendent Eddie Johnson said the officers that crashed didn’t see the construction zone.

“We’re not sure if the construction was properly marked, if someone moved the barriers, we just don’t know,” Johnson said.

They do have dash-cam video.

Mayor Emanuel said it will take some time.

“Most importantly they were out at night doing their job that we asked them to do for all of us and we cannot forget that there’s officers at all times of day doing things for us, making sure that we’re safe. There’s risks associated with it,” Emanuel said.

As of late Thursday morning, the two officers were listed in stable condition.

Henry Clarke heard the crash. He called 911, and quickly went outside to help.

Clarke said he saw “nothing but smoke and steam coming out of the car.”

The officer who had been driving was walking around dazed, according to Clarke, while the other was trapped inside the SUV.

“He was trapped, and there was no ambulances here, no other cop cars,” Clarke said.

Firefighters rescued the officer who was pinned, and paramedics transported both officers to Advocate Christ Medical Center in Oak Lawn in serious condition.

Police said a 33-year-old officer suffered injuries to his left forearm, right leg, and right hip. His partner, a 25-year-old officer, suffered an injury to his right forearm.

Clarke said the two officers were fortunate they weren’t killed.

“The sinkhole was originally about 15 to 20 feet deep, but yesterday they covered it up with some dirt. So that probably saved the police officers, because it was much deeper then what it is now. The car would’ve went all the way down, about 20 feet deep,” he said.

It was not immediately clear what caused the crash. The hole is blocked off on two sides by concrete barricades, and 83rd Street is one-way eastbound at the site of the crash, due to the construction work. The SUV was facing west after the crash.