HELENA, Mont. » Months before Shane Todd’s girlfriend found his body hanging in his Singapore apartment last June, the engineer told his parents he thought his life was threatened and that he was being asked to do something that might hurt U.S. national security.

They were skeptical from the start when a Singapore detective said their son killed himself by setting up an elaborate rope-and-pulley system in his bathroom, then jumping from a chair with a cord around his neck. It was only later they came to believe he had been murdered over his research in New Jersey into material used to make heat-resistant semiconductors, a technology with both civilian and military applications.

Now Rick and Mary Todd’s claims are gaining traction. They have enlisted the help of two U.S. senators to bring their case to the Obama administration’s attention, and they are trying to keep up with numerous media requests spurred by a Financial Times article that broke the story last month. The Singapore government is continuing to investigate, with the FBI pledging assistance.

"We would like a congressional investigation," Mary Todd said Thursday. "We want pressure put on the Singapore government to work with our government to get to the bottom of this and make the truth known."

The Todds traveled from their Marion, Mont., home to Singapore after receiving word of their son’s death, arriving just a few days after his body was found on June 24. In the apartment, they found signs that he was ready to leave Singapore for good the next week: a plane ticket to the U.S., packed clothes, furniture that had been tagged for sale.

Other things didn’t add up. In the bathroom, there was no sign that any ropes and pulleys had been there, Mary Todd said. There were no bolts in the walls, no holes where they might have been, and no evidence that quick repairs had been made to the smooth marble.

Police showed them a suicide note that had been written on Shane Todd’s computer. It was an obvious fake, Mary Todd said, because it thanked his former employer, the Institute of Microelectronics, a company he had grown to hate and had just recently resigned from after working there since 2010, included factually incorrect details and didn’t sound like their son’s writing.

"Absolutely none of it made any sense. I knew at that point that he didn’t write that note. From that point on, I believed he was murdered," Mary Todd said.

It was a chance discovery that convinced them that Todd may have been killed over the research that he that he had been working on for IME. Before they left to go back to the U.S., his parents found what they thought was a speaker for his computer among Todd’s belongings.

"I said to my husband, ‘Can one of the boys use this little speaker? Throw it in the bag,’" Mary Todd said.

It turned out to be a hard drive missed by investigators that contained thousands of documents Todd had backed up from his work computer. After having it analyzed by a computer forensics expert, they found a couple of surprises.

First, the files had been accessed twice soon after their son’s death. Second, the drive contained a draft of a project outline between IME and the Chinese telecom giant Huawei on the development of an amplifier device that utilized a material used in semiconductors called gallium nitride.

Todd had been researching the heat-resistant material that has both civilian uses in products like LED screens and cellphone towers, and military applications in things like radar and satellite systems. He had been trained in New Jersey on proprietary equipment that produces the material but is restricted for export because of the potential military applications.

Rick and Mary Todd said they concluded that Shane Todd had been asked to hand over technology related to his research that he believed would be used to advance Chinese military systems. Shortly before his death, in February 2012, he started expressing concerns to his parents.

"He said, ‘I think they’ve asked me to compromise U.S. security. I feel like I would be betraying my country.’ But he didn’t give us the specifics," Rick Todd said.

He grew more anxious in the weeks leading up to his death, and told his parents to contact the U.S. Embassy if he missed one of their weekly calls, Rick and Mary Todd said.

IME said in a statement that neither Todd nor the company was involved in any classified research project.

Scott Sykes, a Huawei vice president and head of international media affairs, said in a statement the Chinese company "does not do" military equipment or technology, and its research and sales relate only to civil and commercial telecommunications. IME approached the Chinese company once but Huawei decided not to accept and has no "cooperation with IME related to" gallium nitride, Sykes said in the statement.

The Todds asked for a coroner’s inquiry and then hired a pathologist to draw an independent conclusion on the cause of their son’s death. Dr. Edward Adelstein, chief of pathology for the Harry S. Truman Veterans Hospital in Missouri, found that injuries on Shane Todd’s hands showed he had been in a fight.

Adelstein also concluded that Todd was strangled by a binding of some type, then hanged after he had died in order to obscure the actual cause of death.

The Singapore Police Force said in a statement they have asked for the FBI’s assistance in persuading the Todds to share the evidence they have. The FBI has said it will comply with the request, Eric Watnik, spokesman for the US embassy in Singapore, said in a statement.

The Todds said they would feel comfortable handing over the hard drive only if the FBI takes over as the lead agency investigating the death.

They have enlisted the help of U.S. Sens. Max Baucus and Jon Tester of Montana. Baucus met with Secretary of State John Kerry on Thursday to brief Kerry on the situation. He has also met with Singapore’s U.S. ambassador.

"The Todd’s incredible love for their son and commitment to justice is nothing short of inspiring. I saw it in their eyes, and that’s what is driving me to do everything in my power to make sure no stone is left unturned in this case," Baucus said.

AP writers Faris Mokhtar in Singapore and Joe McDonald in Beijing contributed to this report.