BOULDER - Someone tossed a firebomb into a fraternity house about a block from the University of Colorado, setting off a brawl in a nearby alley that sent one man to the hospital, police said.

The firebomb early Friday caused no injuries or significant damage, and residents had put the blaze out by the time firefighters arrived, police spokeswoman Sarah Huntley said.

Huntley said it was probably not a hate crime, but more likely stemmed from a feud between the fraternity and residents of a nearby apartment or with another fraternity. No arrests had been made, and police had no individual suspects.

A jug of charcoal starter fluid with a burning firecracker attached was thrown into the Sigma Alpha Epsilon house through an open door about 2:15 a.m., Huntley said. Someone inside pushed it back out with a wet mop.

"We're very, very fortunate that nobody was hurt," she said.

When officers arrived, they found about 30 young men brawling in the alley, Huntley said. Andrew Hansen, 20, a member of the fraternity, was hospitalized for broken facial bones and a deep cut.

Hansen did not know who hit him, Huntley said.

The fraternity and some residents of a building across the alley have "a history of some problems," including vandalism to a fence at the fraternity house, Huntley said. Sigma Alpha Epsilon members also told investigators of tensions between them and another fraternity.

Jess Havill, vice president of the Sigma Alpha Epsilon chapter, declined to comment.