Without the snap, crackle and pop of fireworks, the Fourth of July would just be a fizzle.

Nevertheless, fire marshals wary of the explosive power of fireworks are urging customers to look for manufacturers' labels at outlets that sell fireworks and to know the laws governing such explosives in their area, to help ensure that the fireworks they buy were properly assembled and can be used safely.

Officials also are asking consumers to be especially careful when lighting fireworks because this area's unusually dry weather has increased the danger of fire.

"I hope people pay attention, because it's so dry out there and if they mishandle fireworks they're going to end up with brush fires," said Maryland Deputy Chief State Fire Marshal Bob Thomas.

Fireworks sold at drugstores, convenience stores and roadside stands generally are reliable, officials said, but they warned against buying fireworks from individuals who sell them from their home or from the trunk of their cars. Those devices, they said, could have been manufactured illegally, often in home factories like the Colmar Manor garage that exploded last Tuesday.

Another increasingly serious problem for law enforcement officials is illegal mail-order fireworks kits, according to John Rogers, a fireworks enforcement officer with the U.S. Consumer Product Safety Commission. The kits contain everything needed to make fireworks, including chemicals that are highly flammable when combined.

The kits usually are distributed through commercial shipping firms that often deliver them unknowingly, Rogers said. Shipping the kits is illegal. Rogers said that anyone buying fireworks should make certain that the product they buy is legal.

"All fireworks that are legal should have the name and address of the manufacturer, and some specific cautions describing what the device does, and also some precautions to follow," he said. "You're not going to find any labels on banned or illegal items."

Buyers should check that the fireworks are labeled Class C, the only kind thatlegally may be sold to the public, he said.

Laws governing fireworks vary from state to state. And in the Washington area regulations may vary between counties. Fire marshals locally said that they will make spot checks of vendors to ensure that the vendors have proper certification and are selling only legally approved fireworks.

All larger firecrackers, including M-80s, cherry bombs and items containing more than 50 milligrams of explosive powder, are illegal under federal law, Rogers said.

Some illegal fireworks, particularly the popular M-80 firecrackers, are extremely dangerous, officials said. The M-80 is one of the items that Prince George's fire investigators believe was being manufactured in the Colmar Manor garage that exploded Tuesday. That fire left two people dead.

Fire officials said they believe that the garage, which contained more than 100 pounds of chemicals, is the largest fireworks plant discovered in Prince George's County. The materials used to make the fireworks were easy to obtain legally, according to fire department spokesman Tony DeStefano.

Ronald Peck, Fairfax County fire battalion chief, said that last year officials did not find anyone selling fireworks in the county without a permit.

"It's very unlikely that someone can make a firework that looks legitimate" enough to sell as legal, Peck said. He warned, however, that even under the best conditions, fireworks can malfunction and cause severe injuries.

Union Memorial Hospital in Baltimore, which houses the Raymond Curtis Hand Trauma Center, has treated at least three fireworks-related accident victims this month. Hospital spokesman Gil Kleiner said that with the upcoming three-day weekend, "people are out barbecueing more, and someone pulls out fireworks and gets careless, not realizing they are playing with explosives."

Surgeon Larry Zachary said most of the fireworks injuries he sees at the center are the result of illegal explosives. Injuries from such blasts are more serious than other types of hand accidents, he said, because soft tissue also is damaged, making it more difficult to reattach and repair damaged fingers.

Peck said fireworks should never be ignited on grass, and observers should stay at least 20 feet away from them. He added that after fireworks have been used, their residue should be disposed of in metal containers filled with water. And he warned against using fireworks in winds of more than 15 mph.

Fire marshals recommended that families wishing to enjoy the Fourth of July holiday attend a fireworks display instead of staging their own.

All types of fireworks, even sparklers, can be dangerous, Maryland Fire Marshall Bob Thomas said.

"The real problem is that everybody likes fireworks, but people who try to use them once a year are not experienced and are careless," he said. "As a result, serious injuries occur, all from mishandling."