DENVER -- A sinkhole about three lanes wide shut down all lanes of northbound Interstate 25, between Interstate 70 and 58th Avenue, Thursday afternoon, causing a huge traffic mess during the evening commute.

Denver Water said that a water pump failed, causing the water to back up and a 66-inch main underneath the highway to burst. The water built up until the roadway collapsed, creating a sinkhole that stretched across the two far right lanes and right shoulder on northbound I-25, near the 58th Avenue exit ramp.

A spokeswoman with the Colorado Department of Transportation said that the hole is 40 feet wide by 60 feet long and about 16 feet deep. No injuries have been reported.

"It's amazing that there wasn't a vehicle involved in this because of the amount of traffic in this area. And I think, if anything good came out of it, it's that," said CDOT spokeswoman Stacey Stegman.

About a half-hour into the mess, at about 3:40 p.m., CDOT allowed drivers stuck in that area to use the High Occupancy Vehicle lane to get through. CDOT also waived the toll fees for the HOV lanes on all stretches of northbound I-25 to alleviate traffic congestion.

However, it took several hours before traffic in that area was cleared. The initial backup stretched several miles. Drivers are encouraged to avoid the area, and Washington Street, Federal Boulevard, Sheridan Boulevard or Broadway as alternate routes.

It is not known when northbound I-25 will reopen, but the highway could be shut down for as long as a week, Stegman said. She said the closure would most likely impact Friday morning's commute.

"Southbound traffic is really going to have to think through their travel plans in the morning. Buses, potentially, could be delayed. Carpools, there's a lot of people that use these lanes now that aren't going to be able to. And so we want them to really plan ahead. Start thinking about their travel times, changing their travel time and looking for alternate routes," Stegman said.

For Friday, northbound drivers can use the HOV lanes for free.

However, those lanes won't be available now to southbounders.

CDOT hopes to reopen at least one lane on northbound I-25 later in the day Friday.

But Stegman said that would be a temporary asphalt fix. Eventually, all that reinforced concrete ripped up by excavators will have to be replaced.

The sinkhole also created cracks that reached across two more highway lanes.

So, by 10 p.m., the work zone had doubled in size.

"We're looking at really expensive repairs," Stegman said. "If you look at the roads, there's sort of a heaving, so they know there is additional damage under that roadway ... There's a lot of asphalt that's unstable in the area."

About 150,000 to 200,000 cars drive through that area daily, and CDOT said opening up I-25, the busiest highway in the state, is their No. 1 priority. Crews from other road projects have been pulled from their jobs so they can help with emergency repairs, Stegman said.

"We know that I-25 is absolutely critical and are going to work 24-7 until we get the road open," Stegman said. "This is a no win situation. No matter what we do we're going to cause major delays in the morning."

Denver Water said approximately 2 million gallons of water leaked from the pipeline, which was built in 1978. In comparison, Denver Water's daily demand this time of year is 115 million gallons.

The water main that broke is part of a major line that provides water to the north end of the city, Denver Water said. But Denver Water said there are no reports of customers without water service -- only some with lower water pressure.

The water in that area has been shut off and the sinkhole has been contained. However, engineers with Denver Water have to first pump out the water and then inspect and repair the pipes before CDOT engineers can completely assess the damage to the highway and evaluate what needs to be done to patch up the road.

Denver Water said it expects to have the water main repaired by Friday morning.

There are reports of some flooding and minor water damage to businesses in that area. A Qwest phone vault also has been affected. Denver Water is working with Qwest officials on that issue.

Gene Foster, owner of Callcomm, about a half block away saw a four foot wave of water rushing towards him. He has ruined two-way radio equipment, water soaked carpet and thousands of dollars in damage.

"It's a big mess," Foster said.

CDOT said it first received calls just before 3 p.m. about a pothole that seemed to be growing.

A water main broke in this same area in May 1997. There was so much water that people ended up going to the roof of the Sofa Mart Furniture Store.

The last time there was a major sinkhole in Colorado was in the summer of 2003 on Interstate 70 near Vail. A large section of the highway was washed away. Repairs took seven weeks.

"This is double that size," Stegman said. "It's by far the largest sinkhole I've ever seen and I've been with the department for 12 years."

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