At least two buildings collapsed as crews battled a massive, multi-alarm fire that destroyed several businesses in Dover's commercial district Monday.

Helicopter footage of the scene showed flames shooting through the roof of one building and thick smoke pouring from the blaze, near West Blackwell and Warren streets. Smoke continued to rise from the burned debris as of late Monday night, some five hours after initial reports of a fire.

Four buildings or portions of the structures collapsed, according to Dover Public Safety Director Daniel DeGroot.

Live video from the scene shared on Twitter captured one building collapse as authorities moved bystanders further away from the scene.

Building collapsed as firefighters battle 7 alarm blaze in downtown Dover. Fire still raging out of control. pic.twitter.com/hhzWx1ednq — Anthony Johnson (@AJohnsonwabc7) October 22, 2018

Multiple area fire departments worked to battle the flames as of 7:15 p.m, he said. There were no reported injuries.

The fire was initially reported around 3:30 p.m. as smoke in Barry's Luncheonette on North Warren Street, according to DeGroot.

NewsCopter 7 is over the scene as firefighters battle a fire in Dover, New Jersey. https://t.co/pFxB7irHWW — Eyewitness News (@ABC7NY) October 22, 2018

"Please stay clear of the area until the fire has been contained and everyone is safe," Dover Mayor James P. Dodd said in a Facebook post shortly after 4 p.m.

#BREAKING: DOVER,NJ (Morris County) - Firefighters on scene of a multiplie alarm fire at 3 N Warren St. Dover Mayor James Dodd told RNJ “4 buildings have collapsed.” pic.twitter.com/YtvFjCADWj — Jay Edwards (@JayEdwardsWrnj) October 22, 2018

Raging 6 alarm fire burns in Dover, NJ. So far no reports of injury but half a dozen towns helping to battle the blaze. pic.twitter.com/ewtDca1vDS — Anthony Johnson (@AJohnsonwabc7) October 22, 2018

Officials could not immediately provide more details. It was unclear how many people were displaced by the blaze. The damaged buildings appeared to include storefronts with apartments above.

Moment the building collapsed in Dover, NJ today during a 7th alarm building fire. Posted by Anthony Preziosi on Monday, October 22, 2018

A spokesman for the Morris County Prosecutor's Office said an investigation was underway, but could not provide more details.

BREAKING: A 7-alarm fire here in #Dover continues to wreak havoc on the city. @DoddMayor tells us every time crews make progress in knocking this fire down, it starts right back up again. Stay tuned for all the latest details tonight on @FiOS1NewsNJ pic.twitter.com/MMnpT2xB19 — Stephen Milewski (@TheSkiReport) October 22, 2018

Noah Cohen may be reached at ncohen@njadvancemedia.com. Follow him on Twitter @noahyc. Find NJ.com on Facebook.