Jesper Joergensen has been charged with 141 counts of arson.
A tornado touched down briefly near the Weston Pass Fire, and the Lake Christine Fire in Basalt continued to grow.
Thousands were out of their homes for the holiday and strict bans on fireworks sought to prevent new fires from igniting in the hot, dry conditions.
The fire had previously burned through 104 structures, including family cabins. It is the third largest in state history.
Fire containment stands at 5 percent as more resources have been added to the fight, including two Air Force MAFFS air tankers.
Jesper Joergensen, 52, acknowledged building a fire on land where he has been living but said he made sure it was out.
US 160 remains closed between Fort Garland and La Veta due to fire activity along the highway.
The Federal Emergency Management Agency said Thursday the U.S. government would help pay the state's cost for fighting the fire.
The fire, which was reported early Wednesday, is zero percent contained.
While Costilla County has only 3,524 residents, due to its unique history it has more than 45,000 landowners, mostly absentee.