St. Paul, Minn. — Members of Minnesota's Congressional delegation toured the oil spill in the Gulf of Mexico on Friday in advance of hearings on capitol hill next week.

The bipartisan group took an aerial tour of the sunken Deepwater Horizon oil rig, the source of the massive spill.

An explosion aboard the Deepwater Horizon oil rig in April caused an oil leak nearly a mile below sea level.

Environmental experts say the oil slick could become one of the nation's worst environmental disasters, threatening hundreds of species of fish, birds and other wildlife along the Gulf Coast.

On Friday, BP lowered a 100-ton concrete-and-steel vault onto the ruptured well in an attempt to begin capturing some of the leaking oil.

The vault, meant to help siphon oil from a blown out Gulf of Mexico well, is settling into the mud over the gusher a mile down.

A BP-chartered vessel lowered the containment box to the sea floor. Workers say it'll need about 12 hours to settle completely.

Underwater robots guided the 40-foot-tall box into place. Once crew determine the box is stable, the robots can hook up a pipe and hose that will funnel the oil up to a tanker.

Senator Amy Klobuchar says BP officials told her it could take as long as 90 days to fully stop the oil leak.

"That is done by drilling another hole into the ocean floor going over into the existing well and then pouring cement into it to cap it off," Klobuchar said. "That will take 90 days and clearly we are not going to be able to wait that long if we are not successful in stopping and stemming some of this oil."

By Sunday, the box the size of a house could be capturing up to 85 percent of the oil. So far about 3 million gallons have leaked in an environmental crisis that's sending toxic oil toward a shoreline of marshes, shipping channels, fishing grounds and beaches.

Klobuchar is demanding that BP pay for the economic and environmental damage caused by the spill.

"They made $16 billion last year; do they have the money to do all of this? Those are the kinds of questions that I think that we really need answers for," she said. "And then, why wasn't there redundancy built in when this piece of equipment, that was supposed to prevent this blow-out from happening, malfunctioned. Why wasn't there some kind of a back up plan?"

Federal officials have expanded an area that is off-limits to fishing because of the oil spill.

The National Oceanic and Atmospheric Administration said Friday an area from the Southwest Pass of the Mississippi River to south of Pensacola, Fla., is now closed.