An effort to prevent the Capital Beltway from turning into a skating rink accidentally turned it into one Friday morning when a contractor pretreating the highway to melt snow mistakenly spread the wrong mixture.

The road was slippery and caused several accidents between the American Legion Bridge and College Park around sunrise. Maryland State Police said troopers responded to 10 crashes on the Beltway between Route 29 and Interstate 270 in the morning. Two people were taken to the hospital with minor injuries, officials said.

"We want to apologize to all the people who were involved in accidents and who were caught in traffic," said Brian Young, head of Maryland's State Highway Administration operations in Montgomery and Prince George's counties. "We are taking this very seriously, and I'm leading an investigation to find out how this happened."

Here's what went wrong:

With the chance of snow forecast for this weekend, and considering last winter's record snowfall, the SHA decided this was a good opportunity to test new plans to pretreat the entire Maryland Beltway instead of focusing primarily on bridges and overpasses.

But there was a mix-up at the Montgomery yard, and two tank trucks - one that carries 6,000 gallons and the other that carries 2,500 gallons - were loaded with liquid magnesium by mistake. The SHA's pretreatment chemical of choice is salt brine - 77 percent water and 23 percent salt.

Liquid magnesium works well for melting packed snow and ice on the road surface, but it's usually mixed with something else when used for that purpose. About 11 p.m. Thursday the two trucks began spraying pure liquid magnesium on the Beltway and up Route 29 to Howard County.

It becomes slick when sprayed on a dry pavement in conditions warmer than the sub-freezing temperatures at which it works best. Not long after the tank trucks were done at 3:45 a.m., the SHA began getting accident reports.

Recognizing the mistake, the agency dispatched salt and sand trucks to counteract the magnesium.

The chance of snow also seems to have slipped away for the weekend.

The forecast now calls for the system to pass south of the Washington region.

Staff writer Maria Glod contributed to this report.