OWASSO, Oklahoma - Three firefighters got hurt Monday trying to put out a huge fire at the Tulsa Asphalt plant near Owasso.

People could see thick black smoke for miles as the fire burned for nearly six hours.

More than 20 emergency vehicles came to fight the fire for hours; three of them were injured when one of the seven tanks exploded.

The fire raged for several hours, as firefighters from several agencies dumped water on the tanks at the Tulsa Asphalt company.

The plan was to keep the tanks cool until the foam trucks could get there.

"The tanks that are involved, there’s three AC tack oil tanks, three burner fuel tanks and one full of diesel fuel," said Rogers County Emergency Manager, Scotty Stokes.

Stokes said none of the materials were highly explosive.

Since the closest fire hydrant was over a mile away, tanker trunks had to constantly leave and come back with more water.

When the foam trucks finally arrived, the fire died down, but that didn’t last long, according to Limestone Fire Chief, Carl Smith.

"For some reason, that safety valve was blocked. And as I said, it had been venting off all through the fire, so when it closed off, the vapors inside started building up the fire from the outside, heating them up until it got to the point where it exploded," Smith said.

As the fire died down, crews moved in closer to fight the flames, which is when the end of one tank blew off and injured three firefighters.

Smith said, "He was in the front of that blast, and so I'm sure he got some heat, got a concussion from that blast."

That fire fighter was a member of the Air Guard firefighting unit. The other injured firefighters - a man and a woman – work for the Limestone Fire Department. All three were taken to the hospital.

The conditions of the firefighters haven't been released, but they are all expected to be OK.

As the rest of the firefighters re-grouped, the fire was finally put out.

We're told two businesses share the property. Becco Asphalt, also known as Tulsa Asphalt, is where the fire started. That company used the Anchor's Quarry to make its asphalt.

The cause hasn't been determined, but company representatives said they are up to code and it appears to be an accident.