State fire investigators searched through debris at the Lodge of the Four Seasons at the Lake of the Ozarks, where an explosion late Thursday injured 17 state employees, one critically, state officials said Friday.

The blast occurred just before midnight at the resort hotel, where a meeting of highway engineers was being held. The hotel is about 130 miles southeast of Kansas City.The explosion was under investigation by the Missouri state fire marshal's office. Initial reports said the blast may have been linked to propane, but a spokeswoman for the fire marshal's office said the cause had not yet been determined.

Wayne Muri, chief engineer for the Missouri Highways and Transportation Department, said all of the injured were employees of the department.

One employee was in critical condition Friday at a Springfield hospital, two were hospitalized in Columbia and four more were being treated at Lake Ozark General Hospital, authorities said.

Besides the employee in critical condition, only one other person was injured seriously, Muri said. He said another 10 employees were treated for minor injuries and released.

Many people who were attending the meeting were moved to other hotels in the area, Muri said.