PITTSBURGH — Pittsburgh officials say they still don't know what caused an explosion that leveled two houses and damaged at least two dozen others.

The explosion happened Friday morning in a vacant house. Though some homes that were damaged were occupied, no one was injured.

A spokesman for Equitable Gas Co. says gas service had been turned off at the vacant home and company inspectors found no leakage from the other destroyed home.

PITTSBURGH — Pittsburgh Public Schools will eliminate 183 jobs next year, most of them teaching positions, because of declining enrollment, officials said.To be cut are 153 teachers, 16 assistant principals and 14 "swim matrons" who help operate the swimming program, Superintendent Mark Roosevelt and Chief Financial Officer Christopher Berdnik said Friday. The cuts are expected to save $10 million.Enrollment this school year is 28,265, down about 1,180 students from 2006-07. Enrollment is expected to decrease by another 1,482 students for the next school year.