An accident at a construction site in San Francisco’s Dogpatch neighborhood this morning sent four workers to the hospital, three with serious injuries, a fire battalion chief said.

The accident was reported at about 8 a.m. at a six-story building under construction at 19th and Illinois streets.

San Francisco fire Battalion Chief Charles Crane said workers were pouring concrete when three men working on the sixth floor fell three stories into the drying concrete.

They were seriously injured, he said.

A fourth worker was also hurt but his injuries were believed to be minor, Crane said.

The California Division of Occupational Safety and Health has been notified of the accident, he said.