Investigators have begun their probe into the Saturday collapse of an overpass segment of the East Sonora Bypass project.

The multi-agency investigation aims to learn why the incomplete bridge suddenly fell about 11:40 a.m., said Robert Spradling, a Caltrans spokesman.

"Nothing has been ruled out so far," he said, including vandalism.

No one was injured in the collapse, which left a crane partially buried under several massive steel beams.

It is too early to determine how the collapse will affect the project's budget, Spradling said. The project's schedule should not be delayed, he said, because it included a cushion of days in case of unforeseen incidents.

Damage was minor because the steel beams were not damaged when they fell, Spradling said.

The investigative team includes representatives from the state Occupational Safety and Health Administration, Caltrans and the project's contractors, R.M. Harris Co. and Goodfellow Bros. Inc.

Citing the ongoing investigation, Spradling said he would not comment on who if anyone witnessed the collapse. He did say there were no crews at the site when the overcrossing fell.

Yesterday, workers were back at the site using a crane to move the fallen beams.

The overcrossing was located just east of the Mono Way-Sanguinetti Road intersection. When complete, it will serve as a portion of Highway 108, overpassing Mono Way, Spradling said.

With Caltrans projects, the contractor normally is responsible for repair costs until state officials have signed off on the completed job, he said.

Following the collapse, authorities received calls that someone might be trapped under tons of steel beams and lumber. Emergency crews, however, determined those reports were untrue.

"We were just pleased to see that no one was trapped under it," said Tuolumne County Fire Marshall Kary Hubbard.