Homeowners got two harsh reminders this week about the perils of hiring unlicensed home improvement contractors:

* In Alexandria on Monday, a contractor who falsely claimed that he had a contractor's license in Virginia pleaded guilty in federal court to wire fraud in a home improvement scam that prosecutors said netted him more than $2.5 million from 68 homeowners.

* In Montgomery County on the same day, TV cameras and reporters followed County Executive Douglas M. Duncan (D) as he toured a house where a contractor stopped in the middle of a $130,000 renovation, leaving the house unlivable. County officials used the house as a backdrop to announce a crackdown on unlicensed contractors.

To avoid being ripped off, officials encourage homeowners to check on licenses with regulators, compare bids and avoid offers of "special deals" and door-to-door solicitations.

Such problems are multiplying as home prices soar and homeowners angle for the lowest prices on additions and repairs, say officials around the region.

Complaints about home remodeling contractors filed with the Better Business Bureau of Metro Washington nearly doubled from 2003 to 2004, jumping from 1,886 to 3,603. In 2002, only 1,300 complaints were filed.

In Montgomery County, complaints of shoddy work by unlicensed contractors have jumped to 58 so far this year, compared with 47 in all of 2004, officials said at a news conference Tuesday. The county has filed criminal charges against unlicensed contractors in 24 recent cases. Ten have been convicted, four are awaiting trial, and there are open warrants against 10.

Montgomery County is also working with law enforcement agencies in other states to extradite unlicensed contractors who left Maryland after committing violations.

Edward J. Johnson III, Better Business Bureau president and chief executive, earlier this week attributed the jump to the increasing numbers of homeowners remodeling because rising home prices have given them equity to take out second mortgages or lines of credit.

Consumer advocates say homeowners are also frequently too eager to pay the least amount possible, too trusting, and not aware of the importance of licensing or of how frequently scams occur.

Senior citizens and first-generation immigrants are often targeted, say consumer groups and regulators.

Maryland residents can check the state Department of Labor, Licensing and Regulation Web site to see if a contractor is licensed. The site is www.dllr.state.md.us. The phone number is 410-230-6309.

Virginia residents can contact county consumer affairs offices, or the state Department of Professional and Occupational Regulation at www.dpor.state.va.us/regulantlookup. The phone number is 804-367-8511.

District residents can check on licenses with the Department of Consumer and Regulatory Affairs at 202-442-4311.

Staff writers Ernesto Londono and Jerry Markon covered the earlier events this week.