Northern California authorities have seized about 15,000 pounds of fireworks and $1 million as part of an investigation into a major distribution line of the illegal explosives.

Authorities across the U.S. West are urging people to forgo fireworks displays as the Fourth of July approaches amid a historic drought and fears of another devastating wildfire season. Fireworks already have caused a few small wildfires, including one started by a child in northern Utah and another in central California.

The San Mateo County Sheriff’s Office says it has linked two people to the sale of fireworks in the county, as well as two residences and a warehouse in Oakland. One of the suspects was booked into jail last week but the other has not yet been taken into custody.

Investigators last week executed search warrants in San Mateo, San Francisco, Alameda and Santa Clara counties.

The major seizure comes months after a massive fireworks explosion left two people dead in Southern California in March and caused at least $3.2 million worth of damage.