Two roofers were electrocuted yesterday in Murrysville and a third critically injured when a 35-foot aluminum pole used for scaffolding escaped their control and came into contact with a 7,200-volt power line.

Despite the efforts of paramedics, who used defibrillators, and several good Samaritans, including a veteran nurse and a pediatrician, two employees with WR Buzz Daily & Son of Greensburg were pronounced dead at Forbes Regional Hospital within an hour of the incident.

The deceased were identified as James Bolen, 52, of Jeannette, and William McNemar, 50, of Turtle Creek. Autopsies will be conducted today by the Allegheny County medical examiner's office, which has custody of the bodies because the hospital where they died is in Monroeville.

Police did not release the name of the third worker, who was badly burned and taken by helicopter to UPMC Mercy. They said he is in his 40s.

An investigator from the U.S. Occupational Safety & Health Administration was on the scene yesterday afternoon at the home at Old William Penn Highway and McCloy Avenue speaking with the company owner, who declined comment.

"Apparently the pole got away from the employees and came in contact with the power line as they were trying to regain control of it," said Robert Szymanski, OSHA's area director in Pittsburgh. "A short duration is enough to kill you. It only takes a second or two to cause an electrical shock."

OSHA's construction standards mandate that equipment that can conduct electricity must be at least 10 feet from power lines.

Part of the agency's investigation will examine the employers' intent and knowledge of the situation, Mr. Szymanski said.

In February, a Coraopolis company, Zeke & Son Roofing and Siding Specialist, was ordered to pay a $50,000 civil fine and a separate $25,000 fine after being convicted in federal court of willful violation of an OSHA regulation.

A worker there was electrocuted in March 2006 when scaffolding touched a power line despite warnings and in violation of OSHA regulations, according to the U.S. attorney's office.

Utilities sometimes take measures to prevent workers from being electrocuted by temporarily fitting power lines with insulated sleeves or even rerouting electricity to another line.

Allegheny Power could not say definitively whether it had been contacted by the roofing company, but police said there was no indication of any protective sleeve on the power line in question.

"Whether you're a contractor or a homeowner, people need to take special safety precautions, just be fully aware of their surroundings and locations of overhead power lines while starting and during work," Allegheny Power spokesman Doug Colafella said.

Although the roofers had been working on the house for roughly a week, one witness said yesterday was the first time they shifted their operation to McCloy Avenue, a side street along which power lines run.

"They just moved to this side," said Lydia Logesky, owner of Rosebud Floral and Giftware across the street from the scene.

When Ms. Logesky left for the nearby bank yesterday morning, everything was fine. She returned several minutes later to a chaotic scene.

"It happened so fast. I saw the scaffolding tipped and all the people everywhere," she said.

The three victims were standing by a steep, grassy strip putting together a pump jack scaffold when the incident occurred around 9:17 a.m.

That type of scaffold consists of two tall poles, each fitted with a jack operated usually by a foot lever, and a platform placed between them. The jacks raise or lower the platform.

Murrysville police Sgt. Charles J. Tappe III said the crew had already put up one of the poles and was working on preparing the other one when there was some sort of problem.

"I guess they lost control of it. It started going back. All three were trying to hold it. Just the tip touched the high-tension wire," Sgt. Tappe said. "Another inch and they would have missed it."

Although the medical examiner has not ruled on an official cause or manner of death for Mr. Bolen or Mr. McNemar, Sgt. Tappe said his department viewed it as an accident. No criminal charges would be forthcoming, he said.

Two other roofing company workers were on the premises at the time, including Mr. McNemar's son. He was on the roof and had the presence of mind to call 911 on his cell phone while coming down a ladder. The other worker climbed back up to the roof after the electrocutions and tied a rope around the second pump jack to stabilize it.

Jane Roberts, 75, a retired nurse from Murrysville, was doing errands when she drove past the site of the incident as it was unfolding.

"I saw one guy on his back on the ground, the second guy had just hit the ground and was flipping over, and somebody was running across the street," she said.

Ms. Roberts said she used triage to pick whom to help first -- the person who was not breathing. She said she did chest compressions on the man, asking a well-dressed man on the scene to do mouth-to-mouth resuscitation.

When the first victim, apparently Mr. Bolen, began coughing after several minutes, Ms. Roberts moved to the next victim. As it turned out, it was Mr. McNemar. She approached a young man near him for help. He was shaking badly.

"I said, 'Pull yourself together. I need your help.' He said, 'OK.' I said, 'Are you sure you can do this?' He said, 'Yes.'"

It wasn't until later that Ms. Roberts learned that the young man was the victim's son.

"We did what we could," Ms. Roberts said, "but God had other plans for them."