OKLAHOMA CITY, Oklahoma - An Oklahoma woman, considered one of the original corporate whistleblowers, died under mysterious circumstances.

Her story sparked a Hollywood movie in the 80s, but to this day, her children still wait for answers about what truly happened to their mother, Karen Silkwood.

“Every year goes by, the less likely we are to find out what happened,” said Karen Silkwood's son Michael Meadows.

On November 13th, 1974, along a stretch of highway about 30 miles north of Oklahoma City, just south of Crescent, Silkwood ran off the road, crashed, and died at the scene.

“I think there was foul play involved,” Meadows said.

He and his sisters, Dawn Lipsey and Kristi, were just kids when their mother died. Too young to understand then, Meadows now believes his mother's death was part of an elaborate cover-up.

“She was hard headed,” Meadows said. “When they pushed, her natural response was to push even harder.”

Silkwood made plutonium pellets for nuclear fuel rods at Kerr-McGee's Cimarron plant a few miles from the crash site.

Silkwood, starring Meryl Streep, detailed Karen's story from her plutonium exposure to investigating alleged wrongdoing at the plant.

“There's been too many people afterward come forward and say what she said was happening,” Meadows said.

Like allegations of manufacturing faulty fuel rods and risking the health of employees with lax safety procedures.

She claims to have gathered evidence to blow the whistle on the dangerous practices at the plant.

“I'm very proud of what she did, who she was, the fact that she stood up when it looked like nobody else was going to,” said Meadows.

“We had heard her voice on a recorder,” said Silkwood's daughter, Dawn Lipsey. “She knew what was going on and they knew she knew.”

There was a recording of Silkwood talking to a union official about the issues at the plant.

The family said she reportedly had a manila folder that contained documentation of her claims when she headed out to Oklahoma City to meet a New York Times reporter.

She never made it and the documents were never recovered at the scene.

“There's people that saw them, what happened to them after that, they don't know,” said Meadows.

Oklahoma police ruled her death a single car accident, but some believe the accident was more sinister - that someone ran her off the road.

“I think whoever covered it up, whether they're still alive or if they've passed on, I think the secret will die with the people that were involved,” Meadows said.

That unanswered secret has left her family without the closure they feel they deserve about a mother they never got to know.

Meadows said, “Not having any memories of my mother, talking about her and what she did, I can talk all day; talking about what I would like to say to her, it's hard.”

“She's a part of my life, that's for sure. I think you just miss what you missed,” said Lipsey.

Silkwood's father sued Kerr-McGee. The company eventually settled for $1.3 million; it closed the plant in 1975.

Oklahoma City-based Kerr-McGee does not exist as a company any more. It was bought-out by Texas-based Anadarko Petroleum for more than $16 billion in 2006.