Vectren is trying to determine if an employee working in the East Side house that exploded Saturday morning did sufficient checks for the presence of natural gas before trying to relight a water heater.

The blast at 3307 Lincoln Ave. killed the resident of the house, Daisy Pauline Hardy, 89, and a friend of Hardy’s who was visiting, Josie Williams, 68.

Mark Rexing, the Vectren employee who lit the match in the house’s basement, was listed Monday in serious condition at Wishard Memorial Hospital in Indianapolis. Rexing has been with Vectren for eight years.

Evansville Fire Department investigator Jesse Storey said gas entered the basement, but its odor was apparently not detectable to Rexing.

According to Storey, Evansville Water Department employees replacing water meters in the area mistook the house’s gas line for its water line.

Storey said they turned off a valve to shut off the line and fractured a plastic pipe that was inside a metal one. The plastic carried the gas and was attached to the home. It branched out of the older metal line, which stopped three or four feet from the basement wall.

Use of plastic pipes is becoming much more common in the natural gas industry, experts say.

“They’re easier to install, more flexible and don’t have the corrosion of metal piping,” said Mark Stultz, a spokes-man for the National Gas Supply Organization. “It’s the dominant means of installation now.”

It’s also common for plastic pipes to be retrofitted for metal ones, according to spokeswoman Daphne Magnuson of the American Gas Association.

Storey said what he thinks happened is the gas, under 55 pounds pressure per square inch, rushed out of the plastic pipe and into the metal one. The metal pipe then allowed gas to migrate toward the resident’s basement.

Natural gas is odorless, but it has an odorant added to alert people to leaks. Storey said the leaked natural gas at the Lincoln Avenue home passed through the ground, as the odorant “was filtered out” in the soil.

Neither Magnuson nor Stultz said they had ever heard of an odorant being filtered out in that manner before, but “that doesn’t mean it couldn’t happen,” Magnuson said.

Vectren employees fixed the broken line and Rexing then went into the house to relight the pilot on the water heater in the basement. Rexing told rescuers that he did not smell gas in the house before the explosion, which occurred when he struck the match, Storey said.

“Our employee obviously made a determination that it was safe to enter the home, and unfortunately the tragedy occurred,” Vectren spokesman Mike Roeder said.

Vectren employees have at their disposal devices that determine the levels of natural gas in the surrounding atmosphere. It hasn’t been determined if Rexing conducted such a test before striking the match, Roeder said, noting that company investigators have not been able to interview him.

Company policy does not specify when such devices are to be used, Roeder said.

“(Employees) obviously have some level of detection equipment with them or on their trucks,” Roeder said. “We use that when in our reasonable judgment there is a potentially unsafe condition. Every situation is certainly different. We certainly provide a high level of training for all of our employees. They’re trained to respond to situations on a case-by-case basis.”

Rexing and two other Vectren employees at the Lincoln Avenue house Saturday morning had a combined 46 years of experience with the company, Roeder said.

Storey said he has a good idea of what occurred at the Lincoln Avenue home, but Roeder said it could be several weeks before Vectren finishes an internal probe.

The explosion occurred at 11 a.m. Saturday. Vectren employees had been called to the home by water department employees at 7:40 a.m.

Vectren attorney Pat Shoulders said the company Sunday negotiated a settlement in a lawsuit brought following the explosion of a Grove Street house in May 2002. A gas line break causing that fire reportedly happened when cable television lines were being installed in front of the home.

Shoulders said the case was settled for “a modest amount” so Vectren executives can focus on the investigation of Saturday morning’s explosion.